Force and Pressure: A Complete Summary of the NCERT Class 8 Physics

1. Define force.
   Force is a push or pull acting upon an object.
2. What is pressure?
   Pressure is the force exerted per unit area on a surface.
3. Give one example of force.
   Lifting a book applies an upward force on it.
4. What is the unit of force?
   The unit of force is the Newton (N).
5. Name one type of contact force.
   Frictional force is a contact force.
6. What happens to the pressure when the area of contact decreases?
   Pressure increases when the contact area decreases.
7. What is the SI unit of pressure?
   The SI unit of pressure is the Pascal (Pa).
8. What is atmospheric pressure?
   Atmospheric pressure is the pressure exerted by the Earth’s atmosphere.
9. Does a sharp knife exert more pressure than a blunt one?
   Yes, a sharp knife exerts more pressure.
10. What is muscular force?
    Muscular force is the force applied by using muscles.
11. What is a non-contact force?
    A non-contact force acts on objects without any physical contact.
12. Give an example of gravitational force.
    An apple falling from a tree is due to gravitational force.
13. What effect does friction have on moving objects?
    Friction slows down or stops moving objects.
14. Name the device used to measure atmospheric pressure.
    A barometer measures atmospheric pressure.
15. Define electrostatic force.
    Electrostatic force is the force exerted by charged objects.
16. Why does a rubber sucker stick to a smooth surface?
    A rubber sucker sticks due to the absence of air, creating a vacuum.
17. Give an example of pressure in liquids.
    Water exerts pressure on the walls of a container.
18. What happens to atmospheric pressure as altitude increases?
    Atmospheric pressure decreases with altitude.
19. Which force is responsible for holding objects down on Earth?
    Gravitational force holds objects down on Earth.
20. What is the relationship between mass and gravitational force?
    Gravitational force increases with mass.

1. What is normal atmospheric pressure at sea level?
   Normal atmospheric pressure at sea level is 101,325 Pa.
2. What force is involved in stretching a rubber band?
   Elastic force is involved in stretching a rubber band.
3. Define contact force with an example.
   A contact force acts only when two objects are physically touching, such as the frictional force.
4. Give an example of air exerting pressure.
   Air-filled tires feel firm because air inside exerts pressure on the tire walls.
5. What happens to liquid pressure with depth?
   Liquid pressure increases with depth.
6. What type of force is gravitational force?
   Gravitational force is a non-contact force.
7. Name one effect of force.
   Force can change the shape of an object.
8. How does pressure vary in fluids at the same depth?
   Pressure in fluids is the same at the same depth in all directions.
9. What is the effect of force on a stationary object?
   A force can set a stationary object in motion.
10. What is magnetic force?
    Magnetic force is the force exerted by a magnet on ferromagnetic materials like iron.
11. What is Pascal’s law?
    Pascal’s law states that pressure applied to a confined fluid is transmitted equally in all directions.
12. Name a device that uses hydraulic pressure.
    A car jack uses hydraulic pressure.
13. What is an example of a non-contact force?
    Gravitational force is an example of a non-contact force.
14. Why does friction produce heat?
    Friction produces heat due to resistance between surfaces.
15. What type of force is needed to stretch a spring?
    Elastic force is needed to stretch a spring.
16. Does liquid pressure act in one direction?
    No, liquid pressure acts in all directions.
17. What happens to pressure if force increases and area is constant?
    Pressure increases if force increases while the area remains constant.
18. What is an effect of atmospheric pressure on boiling water?
    Water boils at a lower temperature at higher altitudes due to lower atmospheric pressure.
19. Define vacuum.
    A vacuum is a space with no matter or very low pressure.
20. Give an example of atmospheric pressure in daily life.
    Drinking from a straw uses atmospheric pressure.
21. What is thrust?
    Thrust is the force exerted perpendicularly on a surface.
22. Why are broad straps used to carry heavy bags?
    Broad straps reduce pressure on the shoulders by distributing the weight over a larger area.
23. How does atmospheric pressure change with altitude?
    Atmospheric pressure decreases as altitude increases.
24. What causes an object to float in water?
    An object floats when the buoyant force is equal to or greater than its weight.
25. What is the SI unit of force?
    The SI unit of force is the Newton (N).
26. Define buoyant force.
    Buoyant force is the upward force exerted by a fluid on an object immersed in it.
27. What is a hydraulic press used for?
    A hydraulic press is used to compress or shape objects.
28. What type of force is frictional force?
    Frictional force is a contact force.
29. Why do we slip on wet floors?
    Wet floors reduce friction, making it easy to slip.
30. What happens to pressure if the area of contact increases while force remains the same?
    Pressure decreases if the area of contact increases.
31. Explain why water pressure increases with depth.
    Water pressure increases with depth because as depth increases, the weight of the water above adds to the force on the water below. This causes greater force per unit area, resulting in higher pressure. Divers experience this increased pressure as they go deeper into the ocean.
32. What are balanced and unbalanced forces?
    Balanced forces are forces acting on an object that are equal in magnitude but opposite in direction, causing no movement. Unbalanced forces are unequal and cause a change in the object’s motion. For example, if two people push a box with equal force from opposite sides, it won’t move, but if one side has a stronger push, the box will move.
33. Describe how pressure is transmitted in fluids.
    According to Pascal’s law, pressure applied to an enclosed fluid is transmitted equally in all directions. This principle is used in hydraulic systems, such as car brakes, where force applied on a small area is transmitted through fluid to exert a larger force on a bigger area.
34. How does friction help in writing?
    Friction between the pen or pencil and paper allows us to write. The resistance provided by the paper helps create marks as the pencil or pen moves across its surface.
35. Why do knives have sharp edges?
    Knives have sharp edges to concentrate the force over a smaller area, increasing pressure. This makes it easier to cut or slice objects by applying less force.
36. Explain the relationship between force, area, and pressure in class 8 physics.
    Pressure is calculated as force divided by area (P = F/A). If the force remains constant and the area decreases, the pressure increases, and vice versa. This is why sharp objects like knives can cut more effectively—they apply force over a smaller area.
37. What are contact forces? Give two examples.
    Contact forces are forces that occur when two objects are in physical contact. Examples include frictional force, which resists motion between surfaces, and applied force, like pushing a table.
38. How does frictional force affect motion?
    Frictional force opposes the movement of objects, slowing them down or stopping them completely. It acts in the opposite direction of the applied force and is a type of contact force.
39. Describe the effects of force on an object in motion.
    A force can change the speed or direction of a moving object, or even stop it. It can also change the shape of an object if applied appropriately.
40. What is gravitational force? Explain with an example.
    Gravitational force is the force of attraction between two objects due to their masses. For example, Earth’s gravity pulls objects toward its surface, which is why we don’t float away.
41. Explain pressure with an example in class 8 physics.
    Pressure is defined as the force applied per unit area (P = F/A). If you press a pencil’s tip against a paper, it makes a dot because the force is concentrated on a small area, resulting in high pressure. But if you press the pencil’s flat end, it leaves no mark because the force spreads over a larger area, reducing pressure. In daily life, high heels create more pressure on the ground compared to flat shoes, which is why they may damage soft surfaces. Pressure plays a vital role in various fields, from engineering to biological processes in the body.
42. Discuss the types of forces with examples as per class 8 physics.
    Forces are broadly classified as contact and non-contact forces. Contact forces require physical interaction, such as friction and muscular force. Friction slows down objects, while muscular force involves body movements, like lifting objects. Non-contact forces act without direct contact, like gravitational force, which pulls objects towards Earth, and magnetic force, which attracts or repels metals. Each type of force affects objects differently based on their nature and direction.
43. Why do the foundations of buildings have a large surface area? Explain using concepts from class 8 physics.
    Foundations of buildings are designed with a large surface area to distribute the building’s weight over a broader area, reducing pressure on the ground. According to the concept of pressure, if the force (weight of the building) is applied over a larger area, the pressure decreases, making the structure more stable. This concept is essential to prevent buildings from sinking into the ground and to ensure stability, especially in soft soil areas.
44. Explain how pressure is created in fluids in class 8 physics.
    Fluids, like liquids and gases, exert pressure in all directions on any surface in contact with them. This is because the particles in fluids are in constant motion and collide with the surfaces around them. For instance, water in a bottle exerts pressure on its walls and bottom. This pressure also increases with depth due to the weight of the water above.
45. What is muscular force? Provide an example.
    Muscular force is the force generated by the muscles in our body. For example, when you lift a bag, you use muscular force to overcome the weight of the bag. This force is essential for performing various daily activities like walking, pushing, and pulling.
46. Describe the role of gravitational force in the solar system.
    Gravitational force keeps the planets in orbit around the Sun. It acts as a centripetal force, pulling planets towards the Sun, balancing their orbital motion. Without gravitational force, planets would drift away instead of maintaining a stable orbit.
47. How does friction benefit us in daily life?
    Friction helps us walk without slipping, keeps objects from sliding, and enables us to write. For instance, friction between shoes and the ground provides grip, preventing us from slipping. It also generates heat and helps in stopping vehicles.
48. What factors affect pressure in liquids?
    Pressure in liquids depends on the depth of the liquid and the density of the liquid. The deeper an object is submerged, the greater the pressure, as more liquid is above it, exerting downward force. Similarly, denser liquids exert more pressure than less dense ones at the same depth.
49. What is the role of air pressure in weather formation?
    Air pressure affects weather by influencing wind and precipitation. High-pressure areas generally bring clear skies, while low-pressure areas are associated with clouds and rain. Air moves from high-pressure to low-pressure areas, creating winds that impact climate patterns.
50. How does a barometer work?
    A barometer measures atmospheric pressure. In a mercury barometer, higher atmospheric pressure pushes mercury up a tube, and lower pressure causes it to fall. This change in mercury levels helps determine weather changes, as pressure shifts indicate different weather conditions.
51. Explain how force can change an object’s direction.
    Force can change the direction of a moving object. For example, when a football player kicks a moving ball in another direction, the force applied alters its path. Similarly, the force of wind changes the direction of a sailboat.
52. Why do we need brakes in vehicles?
    Brakes create friction that slows down or stops a vehicle. When brakes are applied, the frictional force between brake pads and wheels resists motion, converting kinetic energy to heat and stopping the vehicle.
53. Explain why nails have pointed ends.
    Nails have pointed ends to concentrate force over a small area, creating high pressure. This pressure makes it easier to penetrate surfaces, such as wood, with minimal force.
54. Explain atmospheric pressure and its effects on the human body in class 8 physics.
    Atmospheric pressure is the force exerted by the weight of the atmosphere on a surface area. It is about 101,325 Pa at sea level and decreases with altitude. Our bodies are adapted to handle this pressure, with internal fluids exerting an equal force outward. However, rapid altitude changes, like climbing a mountain or flying in an airplane, can affect pressure balance, sometimes causing ear pain or nosebleeds as our bodies adjust to different external pressures.
55. Describe the advantages and disadvantages of friction in class 8 physics.
    Friction has both advantages and disadvantages. It enables us to walk, drive, and perform tasks without slipping, and it helps in holding objects in place. However, friction also produces heat in machines, causing wear and tear on parts, reducing efficiency. For instance, friction in car engines requires lubrication to prevent damage. While friction is beneficial in many situations, controlling it is essential for smooth mechanical operation.
56. How does pressure differ between solid surfaces and fluids as discussed in class 8 physics?
    Pressure on solid surfaces depends on the area and force applied. For example, applying force over a small area, like pressing a pin, creates high pressure. In fluids, pressure acts in all directions and depends on depth and density. Fluids exert pressure uniformly at the same depth, while solids exert pressure only in the direction of the applied force.
57. Discuss the effects of force on the motion and shape of objects.
    A force can cause objects to start moving, speed up, slow down, change direction, or stop. For example, pushing a stationary ball makes it roll. Force can also change the shape of an object, like pressing clay to mold it. In physics, these effects help explain how objects respond to applied forces based on mass, speed, and direction.
58. Explain with an example how non-contact forces can act at a distance.
    Non-contact forces, like gravitational, magnetic, and electrostatic forces, act over a distance without physical contact. For instance, Earth’s gravitational force pulls objects toward its surface, even if they’re at a height. Similarly, a magnet attracts iron objects within its magnetic field without direct contact. This principle is essential in understanding natural phenomena and applications in technology.
59. How is pressure affected by force and area? Explain with examples in class 8 physics.
    Pressure increases with greater force and decreases when applied over a larger area. For example, pressing a pointed nail exerts high pressure, allowing it to penetrate wood easily, while pressing with a flat object spreads force, reducing pressure and preventing damage. In daily life, high heels exert more pressure than flat shoes because they apply force over a small area, which can damage soft floors.
60. Describe how air pressure affects weather and explain with examples.
    Air pressure impacts weather patterns; high-pressure systems usually bring clear, dry weather, while low-pressure systems often result in cloudy, rainy conditions. This is because air moves from high-pressure areas to low-pressure areas, creating wind. For instance, storms occur in low-pressure areas, where warm air rises and cools, leading to precipitation. Air pressure changes also impact altitude-based weather, with lower pressure at high altitudes resulting in cooler temperatures and less oxygen.
61. Explain how pressure is applied in hydraulic systems and give an example in class 8 physics.
    Hydraulic systems work based on Pascal’s principle, which states that when pressure is applied to a confined fluid, it is transmitted equally in all directions. In hydraulic brakes, for example, pressing the brake pedal applies force to a small piston, which increases the pressure in brake fluid. This pressure is transmitted through the fluid to larger pistons, which apply a greater force to the brake pads, stopping the vehicle. This amplification of force is essential in heavy machinery and automobile brakes.
62. What is the role of gravitational force in falling objects?
    Gravitational force pulls objects toward Earth’s center, causing them to fall when unsupported. This force gives objects their weight and varies slightly depending on the object’s distance from Earth. For example, when a ball is dropped, it falls downward due to gravitational force. This force also affects planetary motion, keeping the moon in orbit around Earth and planets around the Sun.
63. How does pressure play a role in blood circulation in humans?
    Blood pressure, generated by the heart’s pumping action, forces blood to circulate through the body. Higher pressure is maintained in arteries, which allows blood to reach all body parts. Veins carry blood back to the heart at a lower pressure. Blood pressure regulation is essential for health, as low or high pressure can affect organ function and overall well-being.
64. Why do mountaineers carry oxygen cylinders while climbing high altitudes?
    At high altitudes, atmospheric pressure is lower, reducing the oxygen concentration in the air. This makes it harder for mountaineers to breathe normally and get enough oxygen. Oxygen cylinders provide a concentrated oxygen supply, ensuring that climbers can breathe effectively in low-pressure, low-oxygen conditions, helping prevent altitude sickness.
65. Explain the concept of buoyancy and why objects float or sink.
    Buoyancy is the upward force exerted by a fluid on an object placed in it. If the object’s weight is greater than the buoyant force, it sinks; if the buoyant force is equal to or greater than the object’s weight, it floats. For example, a boat floats because its shape allows it to displace enough water, generating a buoyant force greater than its weight. This principle is why heavier objects with the right shape, like ships, can float on water.
66. Describe how magnetic force works in terms of attraction and repulsion.
    Magnetic force is the force between magnets and magnetic materials like iron. A magnet has two poles, North and South. Opposite poles attract each other, while like poles repel. This force acts at a distance, allowing magnets to attract objects without touching them. Magnetic force has many uses, including in electric motors, magnetic locks, and data storage.
67. How does friction affect the efficiency of machines? Explain.
    Friction in machines causes resistance between moving parts, generating heat and reducing energy efficiency. For example, friction in an engine causes parts to wear down and heat up, wasting energy. To reduce friction, lubricants are used to allow smoother movement between surfaces, improving efficiency and lifespan of the machine. While friction is sometimes useful, minimizing it is essential for smoother operation in machinery.
68. Explain how the concept of pressure is used in designing dams.
    Dams are built wider at the base to withstand high water pressure, as pressure increases with depth. This structure prevents the dam from collapsing under the weight and pressure of the water. By making the base strong and thick, engineers ensure that the dam can resist the pressure and force exerted by the water, maintaining safety and stability.
69. Discuss why parachutes are used to slow down free-falling objects.
    Parachutes increase the area over which air resistance acts, creating more drag to counteract gravitational pull. This increased air resistance slows the descent of the parachutist, allowing a controlled and safe landing. Without a parachute, gravity would cause the person to fall rapidly, potentially leading to injury upon impact.
70. Explain the relationship between force and pressure in class 8 physics, with examples.
    Pressure is the force applied per unit area. When the force on a surface increases, pressure increases if the area is constant. For instance, standing on a nail creates enough pressure to penetrate skin, while lying on a bed of nails distributes weight over many points, reducing pressure at each point and preventing injury. This concept is used in different applications, from industrial machines to everyday tools, where controlling force and pressure is crucial for effective performance.
71. Explain how air exerts pressure in all directions.
    Air particles are constantly moving and colliding with surfaces, exerting pressure equally in all directions. This is why air pressure inside a balloon acts on every part of the balloon’s surface, causing it to expand evenly. This property of air allows it to fill spaces uniformly and push against surfaces from all angles.
72. What are some applications of Pascal’s law?
    Pascal’s law is applied in hydraulic machines like car brakes, hydraulic jacks, and presses. In car brakes, pressing the brake pedal applies pressure in brake fluid, which transmits to the brake pads, stopping the vehicle. Hydraulic jacks lift heavy objects by applying small force on a piston, which is then amplified and transmitted to a larger piston, lifting the load.
73. Why do we use wheels on carts and luggage?
    Wheels reduce friction by converting sliding friction into rolling friction, which requires less force to move objects. Rolling objects like carts and luggage are easier to move than sliding them, making transportation more efficient and reducing wear on surfaces.
74. Explain how barometers are used to predict weather.
    Barometers measure atmospheric pressure, which helps predict weather patterns. A sudden drop in pressure indicates possible storms or rain, as low pressure allows warm, moist air to rise and cool, forming clouds. High pressure generally means clear, dry weather. Meteorologists monitor pressure changes to forecast weather.
75. Why does friction increase when the surface area of contact is rough?
    Rough surfaces have more irregularities that interlock, increasing resistance to motion. For example, dragging a heavy object across rough concrete requires more force than on smooth tiles, as roughness increases friction. This property of friction is useful in activities that require grip, like rock climbing or using sandpaper.
76. Discuss the different types of friction in class 8 physics.
    There are three main types of friction: static, sliding, and rolling friction. Static friction prevents an object from moving until enough force is applied. For example, a heavy box on the floor needs an initial push to move. Sliding friction occurs when an object slides over a surface, like a book pushed across a table, requiring continuous force to maintain motion. Rolling friction involves an object rolling over a surface, such as wheels on a car, and it is usually weaker than sliding friction, allowing easier movement.
77. Explain how force can change the shape of an object with an example.
    Force can alter an object’s shape by stretching, compressing, or bending it. For example, pressing on clay changes its shape by applying force. Similarly, squeezing a rubber ball compresses it. This concept is used in manufacturing processes where metals and plastics are molded into different shapes using force.
78. Describe how friction can both help and hinder our daily activities.
    Friction is essential for walking without slipping, writing, and driving. For instance, friction between shoes and the ground gives us grip, and friction between tires and the road allows vehicles to stop. However, friction also causes wear and tear on moving parts, like machinery gears, and generates heat, wasting energy. To counteract these issues, lubricants are used to reduce friction in machines and increase their lifespan.
79. How does Pascal’s law apply in hydraulic systems?
    Pascal’s law states that pressure applied to a confined fluid transmits equally in all directions. In hydraulic systems, such as car brakes, force applied on a small piston increases pressure in the fluid. This pressure is then transmitted to a larger piston, generating a greater force to stop the vehicle. Hydraulic lifts and presses use this principle to amplify force, making it possible to lift or compress heavy objects with minimal input.
80. What is atmospheric pressure, and how is it measured?
    Atmospheric pressure is the pressure exerted by the weight of air in the atmosphere on the Earth’s surface. It is measured using a barometer, which often contains mercury. The height of mercury in the barometer tube indicates pressure; at sea level, this is around 76 cm. Changes in atmospheric pressure are vital for weather predictions, as low-pressure systems often bring storms, while high-pressure systems indicate fair weather.
81. Explain why astronauts feel weightless in space.
    Astronauts feel weightless in space because they are in a continuous free fall towards Earth due to gravity. This state of free fall creates a sensation of weightlessness, as both the astronaut and the spacecraft are accelerating at the same rate. In this environment, there is no contact force pushing up on them, like the ground does on Earth, giving the illusion of floating.
82. How does air pressure allow us to drink through a straw?
    When we suck air out of a straw, the pressure inside the straw decreases. The atmospheric pressure outside the straw then pushes the liquid up into the straw to balance the pressure difference. This allows us to drink through the straw, illustrating how atmospheric pressure helps move liquids.
83. What are some factors affecting friction between two surfaces?
    Friction depends on the texture of the surfaces and the force pressing them together. Rough surfaces create more friction than smooth ones, as they interlock with each other. For example, sandpaper creates more friction than ice. Additionally, increasing the force between surfaces, like pressing down harder on an object, increases friction, which is why heavier objects are harder to push.
84. Why do mountaineers experience difficulty breathing at high altitudes?
    At high altitudes, atmospheric pressure is lower, meaning there is less oxygen per unit volume of air. Mountaineers need to take more breaths to get the required oxygen, making breathing difficult. This lower oxygen level can cause altitude sickness, so climbers often carry oxygen cylinders to supplement their intake and help prevent this condition.
85. How does friction affect the motion of a rolling ball on different surfaces?
    The type of surface affects how quickly a rolling ball stops. On rough surfaces like carpet, friction is higher, so the ball slows down faster. On smooth surfaces like ice, friction is low, allowing the ball to roll for a longer distance. This demonstrates how frictional force between surfaces resists motion and varies with surface texture, impacting how objects move.
86. How is force related to motion in class 8 physics? Explain with examples.
    Force is necessary to change the motion of an object, either by starting, stopping, or changing its direction. For example, pushing a stationary toy car sets it in motion. When riding a bicycle, applying force to the brakes slows it down. Additionally, a force applied at an angle, like in a soccer kick, changes the direction of the ball. Newton’s first law, stating that an object will remain at rest or in uniform motion unless acted upon by a force, helps explain this relationship in detail.
87. Explain how fluid pressure works and why it acts equally in all directions.
    In a fluid, pressure results from the constant motion of its particles, which collide with container walls and other particles, distributing force evenly. Since particles in a liquid or gas are free to move, they exert pressure uniformly in all directions. This is why a submerged object experiences pressure from all sides. For example, if you dive underwater, you feel pressure on your entire body, not just from above, as water pressure increases with depth and acts equally on all sides.
88. Discuss the importance of friction in sports.
    Friction is essential in sports for traction, stability, and control. For instance, in soccer, friction between shoes and the ground allows players to run, stop, and change direction quickly. In swimming, reducing friction (drag) is important for speed, which is why swimmers wear streamlined suits. Tennis players rely on friction to control ball spin, and car racers need friction between tires and track for safe, fast turns. Although friction is sometimes reduced, like in skiing, it generally provides control in most sports.
89. How does gravitational force differ from magnetic and electrostatic forces?
    Gravitational force is a non-contact force that acts between masses and is always attractive, such as the force pulling objects toward Earth. Magnetic force, on the other hand, acts between magnets or magnetic materials and can be attractive or repulsive, depending on the poles. Electrostatic force occurs between charged particles; like charges repel, while opposite charges attract. While gravity acts on all objects with mass, magnetic and electrostatic forces depend on specific properties like magnetism or electric charge.
90. Describe an experiment to demonstrate that air exerts pressure.
    A simple way to demonstrate air pressure is by using a glass of water and an index card. Fill the glass with water, place the card over the top, and hold the card in place as you turn the glass upside down. Slowly release the card, and it will stay in place, holding the water. This happens because air pressure outside the glass is greater than the water pressure inside, supporting the card. This experiment shows how air pressure acts against gravity and can hold water in the glass.
91. What are the effects of friction on the environment and energy consumption?
    Friction generates heat and causes wear in machines, leading to energy losses. In cars, friction in engines and tires requires more fuel consumption to overcome, increasing pollution. Lubricants and smoother surfaces are used to reduce friction and energy waste in machines. However, reducing friction excessively can also lead to less control, as in icy roads, which require salt or sand to create traction. Balancing friction is essential to improve efficiency, reduce pollution, and maintain safety in various applications.
92. Explain how the size and shape of an object affect its buoyancy in a fluid.
    Buoyancy depends on the amount of fluid an object displaces. A larger object displaces more fluid, creating a greater buoyant force. Shape also matters; a flat, wide shape like a boat allows it to float because it displaces enough water to support its weight. Even if the object is heavy, such as a steel ship, its shape can allow it to displace a sufficient volume of water to stay afloat. Compact shapes, like a solid metal ball, may sink as they don’t displace enough fluid relative to their weight.
93. How do non-contact forces play a role in everyday life? Provide examples.
    Non-contact forces, like gravitational, magnetic, and electrostatic forces, impact daily life significantly. Gravity keeps us anchored to the Earth, while magnetic forces are used in compasses to navigate by aligning with Earth’s magnetic field. Electrostatic force, observed when clothes stick together in a dryer, occurs because of electric charge build-up. In technology, magnets are used in hard drives, and gravity enables activities from driving to sports by providing consistent force.
94. Discuss how force and pressure differ, using real-life examples.
    Force is an interaction that changes the motion or shape of an object, while pressure is the force applied per unit area. For example, a person standing on soft ground exerts force, but wearing heels increases pressure, causing the heels to sink into the ground. A bulldozer blade, applying force over a wide area, pushes soil with high force but lower pressure than a narrow shovel, demonstrating how area affects pressure distribution. Understanding this distinction is critical in designing tools, vehicles, and machinery.

95. Describe an experiment to show the existence of atmospheric pressure.
Take an empty can, add a little water, and heat it until steam forms. Quickly seal the can with a cap and place it in cold water. The can collapses inward as steam condenses, creating a vacuum inside. The higher atmospheric pressure outside crushes the can, proving that air exerts pressure. This experiment vividly demonstrates atmospheric pressure, especially the force exerted by air when internal pressure is significantly reduced.