Questions and Answers
What are contact forces?
Contact forces are forces that come into play when two objects are in physical contact with each other.
What are non-contact forces?
Non-contact forces are forces that act on objects without any physical contact between them.
Name two examples of contact forces.
Muscular force and frictional force.
What happens when you kick a ball?
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How does force affect a spring when stretched?
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List two effects of force on objects.
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What is meant by the resultant force (net force)?
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What happens to the movement of an object when equal forces are applied in opposite directions?
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What is the unit of force?
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What is required for a body to be in motion?
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Describe what balanced forces are.
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What typically happens when two people push a heavy object in the same direction compared to pushing alone?
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What will happen if one person pushes a table from one side and another person pushes it from the opposite side with equal force?
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In a game of tug of war, if both teams pull with equal forces, what will happen to the rope?
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What is the definition of force?
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How is force denoted, and what is its SI unit?
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What happens when equal forces act on an object from opposite directions?
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Describe the resultant force when unequal forces act in the same direction.
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What is the direction of the resultant force when unequal forces act in opposite directions?
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What do you conclude when a table is easier to push with two people rather than one?
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Why might an object not move even if a force is applied?
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What is required for a cycle to start moving when someone sits on it?
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What is the resultant force when a 10 N force and a 20 N force act together in the same direction?
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Identify the type of force that is applied when two objects are in contact.
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What type of force can produce motion in a stationary object?
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Which force can change the direction of a moving object?
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Name a force that can stop a moving object.
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What is the resultant force when a 10 N force and a 50 N force act together in the same direction?
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List two examples of non-contact forces.
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How does increasing the force applied to the pedal of a bicycle affect its speed?
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Why do camels have broad feet?
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Why do nails and thumb pins have pointed tips and flat heads?
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Why do backpacks and carry bags have broad straps?
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What is the formula for calculating pressure?
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Why do porters and construction workers place a round piece of cloth on their heads when carrying heavy loads?
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If a force of 50 N is applied on an area of 25 m², what is the pressure exerted?
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Why are the foundations of buildings and dams kept wide?
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How does pressure change if you increase the force applied on a constant area?
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Why do high heels make us feel uncomfortable while walking on the ground?
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What is lateral pressure in liquids?
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Convert an area of 500 cm² to m².
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What two factors affect the pressure at a point in a liquid?
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What is the SI unit of pressure?
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Given a pressure of 200 Pa and a force of 40 N, calculate the area on which the force acts.
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What type of force is applied when lifting a school bag?
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Why is frictional force considered a contact force?
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What causes a bicycle to slow down and finally stop when you stop pedaling?
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Name a force that can act over a distance without direct contact.
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What is the force called that a magnet exerts on some iron pins?
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What happens when like poles of two magnets are brought close to each other?
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Why are we able to walk without slipping?
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What type of force is experienced when pushing a cart?
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Why is it easier to cut fruits and vegetables with a sharp knife than with a blunt one?
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What happens when you push the sharpened end of a pencil into moist soil compared to the unsharpened end?
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In the lab activity with a pencil and soil, what conclusion can be drawn regarding the effect of force?
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If the area of contact is reduced while keeping the same force applied, what happens to the pressure?
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How does the area of contact affect the penetration of an object, such as a pencil, into a material?
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What can be inferred from the observation that the sharpened end of a pencil pushes into the soil more easily?
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What happens to the water flow when holes are punched at the same depth in a plastic bottle?
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How will water flow from holes punched at different depths in a plastic bottle?
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Why do dams have thick walls at the bottom?
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What is the relationship between liquid pressure and depth?
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How does blowing air into a balloon demonstrate gas pressure?
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Where is atmospheric pressure the highest on Earth?
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How does atmospheric pressure change as altitude increases?
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Why are water supply tanks in an area constructed higher than the buildings they serve?
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What is liquid pressure?
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Define atmospheric pressure.
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What is electrostatic force?
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How can you demonstrate that electrostatic force is a non-contact force?
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What do like charges do when they are near each other?
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What do unlike charges do when they are near each other?
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How can you show that magnetic force is a non-contact force?
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What is gravitational force?
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Why does a ball thrown up in the air come back down?
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What force opposes the motion of a moving object?
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Study Notes
Forces
- A force is a push or pull that can cause an object to change its motion or shape.
- Forces can be either contact forces or non-contact forces.
Resultant Force (Net Force)
- When forces are applied in the same direction, the resultant force is the sum of all the forces.
- When forces are applied in opposite directions, the resultant force is the difference between the two forces.
- If the two opposing forces are equal, the resultant force is zero, and the object will not move.
Direction of Force
- The direction of force is the direction in which a force is applied on an object.
- It is not necessary that the direction of force is the same as the direction of motion.
Calculate the Force
- The resultant force can be calculated by adding or subtracting the forces acting on an object.
Effects of Force
- Force can produce motion in a stationary object.
- Force can stop a moving object.
- Force can change the direction of a moving object.
- Force can change the speed of a moving object.
- Force can change the size and shape of an object.
Types of Forces
- Contact forces: forces that come into play when objects are in physical contact with each other (e.g., muscular force, frictional force).
- Non-contact forces: forces that do not require physical contact between objects (e.g., magnetic force, electrostatic force, gravitational force).
Muscular Force
- Muscular force is the force produced by the muscles of our body while pushing or pulling.
- It is a type of contact force.
Frictional Force
- Frictional force is the force that opposes the motion of an object.
- It is a contact force that arises when the surfaces of the objects are in contact with each other.
Non-contact Forces
- Magnetic force: the force exerted by a magnet on another magnet or magnetic material.
- Electrostatic force: the force exerted by a charged object on another charged or uncharged object.
- Gravitational force: the force that attracts two objects with mass towards each other.
Pressure
- Pressure is the force acting on a unit area of a surface.
- Pressure is inversely proportional to the area of contact.
- The smaller the area of contact, the greater is the pressure exerted.
Applications of Pressure
- A camel has broad feet to walk easily on sand.
- Nails and thumb pins have pointed tips to pierce surfaces easily.
- Backpacks and carry bags have broad straps to reduce pressure on hands and shoulders.
Pressure Exerted by Liquids
- Liquids exert pressure on the base and walls of the container.
- The pressure exerted by a liquid at any point inside it increases with the increase in depth.
- The pressure due to a liquid is directly proportional to density.
Factors Affecting Liquid Pressure
- Height of the liquid column
- Density of the liquid### Gas and Liquid Pressure
- Particles in an inflated balloon are continuously moving and exert gas pressure.
- Pressure on the walls of a container is referred to as liquid pressure.
Atmospheric Pressure
- The air surrounding us is a mixture of various gases that exerts atmospheric pressure.
- Atmospheric pressure is the pressure exerted by the weight of the air.
- It is maximum at sea level due to the enormous amount of pressure.
- As altitude increases, atmospheric pressure decreases.
- Atmospheric pressure at a place depends on its altitude from sea level.
- It balances the effect of water pressure.
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Description
Understand how forces interact with objects, and how they can be combined to produce a resultant force. Explore how forces can make objects move or stay still.