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Q1. A push or a pull on an object is called:
In physics, a push or a pull on an object is defined as a force. Force is the interaction that can change the state of motion, direction, or shape of an object. Pressure is force per unit area, friction is a force that opposes motion, and motion is the change in position of an object.
Q2. Which of the following is an example of a contact force?
Muscular force is a contact force because it acts only when two objects are in physical contact, such as when you push a cart or lift a weight. Gravitational, magnetic, and electrostatic forces are non-contact forces and act even without physical contact between objects.
Q3. What is the SI unit of force?
The SI unit of force is the newton (N), named after Sir Isaac Newton. One newton is the force required to give a mass of 1 kilogram an acceleration of 1 m/s². Pascal is the unit of pressure, Joule is the unit of work and energy, and Watt is the unit of power.
Q4. Forces are due to an _____ between two objects.
Forces are always due to an interaction between two objects. When one object exerts a force on another, the second object also exerts a force back (Newton’s Third Law). This interaction can be contact-based or non-contact (like gravitational or magnetic forces).
Q5. Which of the following is a non-contact force?
Magnetic force is a non-contact force because a magnet can attract or repel another magnet or iron object without touching it. Friction, muscular force, and mechanical force are all contact forces that require physical contact between surfaces.
Q6. The force that opposes motion between two surfaces in contact is called:
Friction is the force that opposes the relative motion between two surfaces in contact. It acts in the opposite direction to the motion or the tendency of motion. Gravitational force pulls objects towards Earth, magnetic force acts between magnets, and pressure is force per unit area.
Q7. A ball at rest on the ground will remain at rest unless:
According to Newton’s First Law of Motion, an object at rest stays at rest unless acted upon by an unbalanced external force. A ball will not move on its own; it needs a push or pull (force) to change its state of motion. Time and weather do not directly cause motion.
Q8. Which force is responsible for pulling objects towards the Earth?
Gravitational force is the attractive force exerted by the Earth on all objects, pulling them towards its centre. This force is responsible for the weight of objects and the falling of things to the ground. Magnetic, electrostatic, and muscular forces do not pull objects towards the Earth.
Q9. Pressure is defined as:
Pressure is defined as the force acting perpendicularly on a surface divided by the area over which the force is spread. The formula is P = F/A. It measures how concentrated a force is. Force multiplied by area is not a standard definition, and force times distance is work.
Q10. What is the SI unit of pressure?
The SI unit of pressure is the pascal (Pa), named after Blaise Pascal. One pascal is equal to one newton per square metre (1 Pa = 1 N/m²). Newton is the unit of force, Joule is the unit of energy, and Watt is the unit of power.
Q11. Which of the following tools has a sharp edge to increase pressure?
A knife has a sharp edge with a very small area. When the same force is applied over a smaller area, the pressure increases (P = F/A). This high pressure allows the knife to cut easily. Wide straps and tracks decrease pressure, and a sleeping bag is not a cutting tool.
Q12. Which force is applied when you kick a football?
When you kick a football, the force applied is muscular force. It is a contact force generated by the contraction of muscles in your leg. Magnetic, electrostatic, and gravitational forces are non-contact and are not involved in kicking a ball.
Q13. A moving cricket ball is stopped by a fielder. This is an example of:
When a fielder catches a moving cricket ball, the force applied by the fielder’s hands changes the speed of the ball from moving to zero (stops it). This is an example of a force changing the speed (and state of motion) of an object. It also changes direction slightly, but the primary effect is stopping it.
Q14. Which of the following is a contact force?
A horse pulling a cart is a contact force because the horse must be in physical contact with the cart to pull it. Magnetic attraction, electrostatic attraction, and gravitational force (falling ball) are all non-contact forces that act without physical contact.
Q15. Liquids exert pressure:
Liquids exert pressure in all directions—downwards, upwards, and sideways. The pressure at a point in a liquid acts equally in all directions. This is why a liquid takes the shape of its container and exerts pressure on the bottom, sides, and top (if a solid is immersed).
Q16. The atmospheric pressure at sea level is approximately:
Atmospheric pressure at sea level is approximately 1.01 × 10⁵ Pa (about 100,000 Pa or 1 atm). This is the pressure exerted by the weight of the air column above us. 1 Pa is very small, 100 Pa is too low, and 1 N is a unit of force, not pressure.
Q17. When you squeeze a sponge, its shape changes. This shows that force can:
Squeezing a sponge changes its shape because the applied force causes deformation. This is a classic example of force changing the shape of an object. The sponge is stationary, so its state of motion is not changed, and direction is not relevant here.
Q18. Electrostatic force is a:
Electrostatic force is a non-contact force because it acts between charged bodies without them touching. For example, a rubbed comb attracting paper pieces works even without contact. Contact forces require physical interaction, while electrostatic, magnetic, and gravitational forces do not.
Q19. Friction always acts:
Friction always opposes the relative motion between two surfaces in contact. It acts in the direction opposite to the motion (or the tendency of motion). This is why a ball rolling on the ground slows down and stops—friction acts opposite to its motion.
Q20. Which of the following increases friction?
Making a surface rough increases friction because rough surfaces have more interlocking irregularities. Ball bearings, oil/grease, and air cushions are methods used to reduce friction by providing smooth surfaces or lubrication. Rough surfaces create more resistance and hence more friction.
Q21. A push or pull applied by a machine is called:
A force applied by a machine (like a motor, engine, or lever) is called mechanical force. Muscular force comes from living beings, gravitational force is from the Earth, and magnetic force is from magnets. Machines transmit energy to apply mechanical force.
Q22. The pressure exerted by a liquid:
The pressure exerted by a liquid increases with depth because the weight of the liquid above a point increases. The deeper you go, the greater the pressure. This is why dams are wider at the bottom—to withstand higher pressure. Pressure does not remain constant or decrease with depth.
Q23. Which of the following is an example of a pull?
Opening a drawer involves pulling the handle towards you, so it is an example of a pull. Hitting a nail (push), kicking a ball (push), and pushing a shopping cart (push) are examples of pushes. Pulls and pushes are both forces, but they act in opposite directions.
Q24. A horse pulling a cart is an example of:
A horse pulling a cart uses its muscles to apply force, which is muscular force. It is a contact force because the horse is physically connected to the cart via a harness. Electrostatic, gravitational, and non-contact forces do not apply here. The horse’s muscles generate the force needed to move the cart.
Q25. Which of the following is a non-contact force?
A magnet attracting a nail is a non-contact force because the magnet can attract the nail without touching it. Pushing a wall, pulling a rope, and lifting a bucket all require physical contact, so they are contact forces. Magnetic force acts at a distance.
Q26. Why do school bags have wide straps?
Wide straps increase the area of contact with the shoulder. For the same force (weight of the bag), a larger area reduces the pressure (P = F/A). This makes the bag more comfortable to carry. Narrow straps would concentrate the force and cause more pressure and discomfort.
Q27. The force that pulls objects towards the center of the Earth is called:
Gravitational force is the attractive force that the Earth exerts on all objects, pulling them towards its centre. This force is responsible for the weight of objects and the falling of things to the ground. Muscular, magnetic, and frictional forces are different types of forces.
Q28. When you inflate a balloon, the air inside exerts pressure:
Gases, like liquids, exert pressure equally in all directions. The air molecules inside the balloon collide with the inner walls of the balloon, exerting pressure on all sides. This is why the balloon expands uniformly and does not just bulge in one direction.
Q29. Which of the following is an example of force changing the direction of motion?
When a batsman hits a ball, the force of the bat changes the direction of the ball’s motion (and also its speed). This is an example of force changing the direction of motion. Catching a ball changes speed (stops it), shaping clay changes shape, and stretching a spring changes shape.
Q30. The force exerted by a magnet on an iron nail is an example of:
The force exerted by a magnet on an iron nail is magnetic force. It is a non-contact force that attracts ferromagnetic materials like iron. Electrostatic force is between charged bodies, gravitational force is due to mass, and muscular force is from muscles. Magnetic force is the correct answer.
Q31. What happens to the pressure if the area of contact increases while the force remains the same?
Pressure is inversely proportional to area (P = F/A). If the area of contact increases and the force stays constant, the pressure decreases. This is why wide straps and broad tyres reduce pressure. Increasing area spreads the force over a larger region, reducing its effect per unit area.
Q32. Our atmosphere exerts pressure on our head. Why are we not crushed by it?
The atmospheric pressure is balanced by the pressure exerted by the fluids inside our body (blood, water, etc.), which push outwards. This internal pressure counteracts the external atmospheric pressure, so we do not feel crushed. Atmospheric pressure is not zero, our head is not hard enough alone, and gravity does not cancel it.
Q33. Which of the following is an example of a push?
Closing a door involves pushing it to move it. Drawing a curtain and lifting a backpack involve pulling, and plucking a guitar string involves a pull on the string. Pushes and pulls are opposite actions; pushing moves objects away, while pulling brings them closer.
Q34. The force that acts between two charged bodies is called:
The force that acts between two charged bodies is electrostatic force. It can be attractive (opposite charges) or repulsive (like charges). Magnetic force acts between magnets, gravitational force acts between masses, and frictional force opposes motion. Electrostatic force is the correct answer.
Q35. Why do tractors have broad tyres?
Tractors have broad tyres to increase the area of contact with the ground. This decreases the pressure exerted on the soft soil, preventing the tractor from sinking. Broad tyres spread the weight over a larger area, reducing pressure. This is the same principle as wide straps.
Q36. Which of the following forces is always attractive?
Gravitational force is always attractive, pulling objects towards each other. Magnetic force can be attractive or repulsive, electrostatic force can also be attractive or repulsive, and frictional force opposes motion. Gravity never repels; it only attracts objects with mass.
Q37. When a spring is stretched, its shape changes. This is due to:
When a spring is stretched, an applied force (like pulling) changes its shape. This is an example of a force causing deformation. Friction opposes motion, magnetic force is from magnets, and electrostatic force is from charges. An applied force is the direct cause of the shape change.
Q38. The pressure exerted by a gas is due to:
Gas pressure is caused by the continuous collisions of gas particles with the walls of their container. The particles bounce off the walls, exerting a force per unit area. Weight, colour, and smell do not cause pressure. The kinetic theory of gases explains this.
Q39. Which of the following is not a contact force?
Electrostatic force is a non-contact force that acts between charged bodies without physical contact. Friction, muscular force, and mechanical force all require contact between objects. Electrostatic force is the correct answer as it is the only non-contact force among the options.
Q40. A potter changes the shape of a clay pot by applying force. This is an example of:
When a potter applies force to clay, the clay deforms and takes a new shape. This is a direct example of force changing the shape of an object. Speed, state of motion, and direction are not involved here; the clay is stationary and the force is used to mould it.
Q41. The force responsible for the falling of raindrops to the ground is:
Raindrops fall to the ground due to the gravitational force of the Earth, which pulls them downwards. Magnetic force acts on magnetic materials, electrostatic force acts on charges, and atmospheric pressure is not the cause of falling raindrops (it actually acts in all directions). Gravity is the correct force.
Q42. Friction is caused by:
Friction is caused by the irregularities (roughness) on the surfaces in contact. Even apparently smooth surfaces have microscopic bumps and valleys that interlock, creating resistance. Smooth surfaces have fewer irregularities and less friction. Colour and temperature do not cause friction directly.
Q43. A ball rolling on the ground stops after some time because of:
A ball rolling on the ground stops due to friction between the ball and the ground. Friction opposes the motion and gradually slows the ball down until it stops. Gravitational force pulls it downwards, but friction is the force that stops the horizontal motion.
Q44. Which of the following increases pressure?
Pressure is inversely proportional to area (P = F/A). If the area decreases while the force remains constant, the pressure increases. This is why sharp objects (with small area) exert high pressure. Increasing area decreases pressure, and changing force affects pressure differently.
Q45. Which force is used to separate iron pins from a mixture using a magnet?
A magnet is used to separate iron pins from a mixture because the magnet exerts a magnetic force on the iron pins, attracting them. Gravitational, muscular, and frictional forces are not involved in this separation process. Magnetic force is the correct answer.
Q46. The walls of a dam are made wider at the bottom because:
The pressure exerted by water increases with depth. The bottom of a dam experiences the highest pressure because of the weight of the water above. To withstand this high pressure, the walls are made wider and stronger at the bottom. Aesthetics and storage capacity are not the primary reasons.
Q47. When a force is applied to a stationary object, it can:
A force applied to a stationary object can set it into motion (if it is enough to overcome inertia). It may also change its shape or stop it, but the primary effect on a stationary object is to start its movement. The question asks for one possible effect, and setting into motion is the most direct.
Q48. Which of the following is an example of electrostatic force?
A rubbed plastic comb gains static charge and attracts small paper bits. This is an example of electrostatic force. A nail sticking to a magnet is magnetic force, a stone falling is gravitational force, and pushing a bicycle is muscular force.
Q49. The weight of an object is the force with which it is pulled towards the Earth. This force is:
Weight (W = mg) depends on the value of g (acceleration due to gravity), which varies from planet to planet. On Earth, g is about 9.8 m/s², but on the Moon it is about 1.6 m/s², so the weight is different. Mass is the same everywhere, but weight changes. Weight is directly related to gravity.
Q50. A person is not able to move a heavy almirah despite pushing it. Which force is preventing the motion?
The force preventing the almirah from moving when pushed is friction between the almirah and the floor. Friction opposes the applied force up to a maximum limit (static friction). If the applied force is less than the static friction, the object does not move. Gravitational, electrostatic, and magnetic forces are not the primary opposing forces here.