In physics, a force is defined as any interaction that, when unopposed, will change the motion of an object. It is essentially a push or a pull.
Q2. Which of the following is an example of a contact force?
• Gravitational force
• Magnetic force
• Muscular force
• Electrostatic force
Answer: Muscular force
Muscular force is applied when our muscles are in contact with an object, like lifting a book. Gravitational, magnetic, and electrostatic forces can act without direct contact.
Q3. What is the SI unit of force?
• Pascal
• Joule
• Watt
• Newton
Answer: Newton
The SI unit of force is the Newton (N), named after the famous scientist Sir Isaac Newton.
Q4. Forces are due to an _____ between two objects.
• attraction
• repulsion
• interaction
• separation
Answer: interaction
A force cannot exist on its own. It always results from the interaction of one object with another.
Q5. Which of the following is a non-contact force?
• Friction
• Muscular force
• Magnetic force
• Mechanical force
Answer: Magnetic force
A magnetic force can attract or repel objects without physically touching them, making it a non-contact force.
Q6. The force that opposes motion between two surfaces in contact is called:
• Gravitational force
• Magnetic force
• Friction
• Pressure
Answer: Friction
Friction is a contact force that resists the relative motion or tendency of motion between two surfaces in contact.
Q7. A ball at rest on the ground will remain at rest unless:
• It is left undisturbed
• A force is applied on it
• Time passes
• The weather changes
Answer: A force is applied on it
According to Newton’s first law of motion, an object at rest stays at rest unless acted upon by an unbalanced force.
Q8. Which force is responsible for pulling objects towards the Earth?
• Magnetic force
• Electrostatic force
• Gravitational force
• Muscular force
Answer: Gravitational force
Gravitational force is the non-contact force exerted by the Earth that pulls all objects towards its center.
Q9. Pressure is defined as:
• Force multiplied by area
• Force divided by area
• Area divided by force
• Force times distance
Answer: Force divided by area
Pressure is the amount of force applied perpendicularly on a unit area. The formula is P = F/A.
Q10. What is the SI unit of pressure?
• Newton
• Joule
• Pascal
• Watt
Answer: Pascal
The SI unit of pressure is the Pascal (Pa), which is equal to one Newton per square meter (N/m²).
Q11. Which of the following tools has a sharp edge to increase pressure?
• A school bag with wide straps
• A knife
• A tank with wide tracks
• A sleeping bag
Answer: A knife
A knife has a sharp, small area of contact. For the same applied force, a smaller area creates higher pressure, allowing it to cut easily.
Q12. Which force is applied when you kick a football?
• Magnetic force
• Electrostatic force
• Muscular force
• Gravitational force
Answer: Muscular force
Kicking a football involves the contraction and expansion of muscles, which applies a contact force on the ball.
Q13. A moving cricket ball is stopped by a fielder. This is an example of:
• Force changing the speed of an object
• Force changing the shape of an object
• Force changing the direction of an object
• Force causing no change
Answer: Force changing the speed of an object
The fielder applies a force that reduces the speed of the moving ball from its initial speed to zero, thus changing its state of motion.
Q14. Which of the following is a contact force?
• A magnet attracting iron nails
• A comb attracting tiny paper pieces
• A ball falling to the ground
• A horse pulling a cart
Answer: A horse pulling a cart
The horse is physically attached to the cart and applies muscular force through the harness, which is a contact force.
Q15. Liquids exert pressure:
• Only downwards
• Only upwards
• Only sideways
• In all directions
Answer: In all directions
Liquids exert pressure on the walls of their container in all directions—downwards, upwards, and sideways.
Q16. The atmospheric pressure at sea level is approximately:
• 1 Pascal
• 10⁵ Pascal
• 100 Pascal
• 1 Newton
Answer: 10⁵ Pascal
Atmospheric pressure at sea level is about 101,325 Pascals, which is approximately 10⁵ Pa or 1 bar.
Q17. When you squeeze a sponge, its shape changes. This shows that force can:
• Change the state of motion
• Change the direction of motion
• Change the shape of an object
• Stop a moving object
Answer: Change the shape of an object
When force is applied to a sponge, its original shape is deformed, demonstrating that force can alter the shape of an object.
Q18. Electrostatic force is a:
• Contact force
• Non-contact force
• Muscular force
• Mechanical force
Answer: Non-contact force
Electrostatic force is the force exerted by charged objects on other charged or neutral objects without physical contact.
Q19. Friction always acts:
• In the direction of motion
• Opposite to the direction of motion
• Perpendicular to the direction of motion
• Downwards
Answer: Opposite to the direction of motion
Friction opposes the relative motion between two surfaces, so it acts in the direction opposite to the motion or attempted motion.
Q20. Which of the following increases friction?
• Using ball bearings
• Applying oil or grease
• Making the surface rough
• Using air cushions
Answer: Making the surface rough
Rough surfaces have more irregularities that interlock with each other, creating greater frictional force.
Q21. A push or pull applied by a machine is called:
• Muscular force
• Mechanical force
• Gravitational force
• Magnetic force
Answer: Mechanical force
Mechanical force is the force applied by machines or tools, such as the force exerted by a motor or a lever.
Q22. The pressure exerted by a liquid:
• Decreases with depth
• Increases with depth
• Remains the same at all depths
• Is independent of depth
Answer: Increases with depth
The weight of the water column above increases with depth, causing the pressure exerted by the liquid to increase as depth increases.
Q23. Which of the following is an example of a pull?
• Hitting a nail with a hammer
• Opening a drawer
• Kicking a ball
• Pushing a shopping cart
Answer: Opening a drawer
Opening a drawer involves pulling it towards yourself to move it out of its original position.
Q24. A horse pulling a cart is an example of:
• Non-contact force
• Muscular force
• Electrostatic force
• Gravitational force
Answer: Muscular force
The horse uses its muscles to apply a force on the cart through the harness.
Q25. Which of the following is a non-contact force?
• A boy pushing a wall
• A girl pulling a rope
• A magnet attracting a nail
• A man lifting a bucket
Answer: A magnet attracting a nail
The magnet exerts a force on the iron nail without touching it, which is a characteristic of a non-contact force.
Q26. Why do school bags have wide straps?
• To increase pressure on the shoulder
• To decrease pressure on the shoulder
• To make the bag look stylish
• To increase weight
Answer: To decrease pressure on the shoulder
Wide straps increase the area of contact. For the same force (weight of the bag), a larger area results in lower pressure, making it more comfortable.
Q27. The force that pulls objects towards the center of the Earth is called:
• Muscular force
• Magnetic force
• Gravitational force
• Frictional force
Answer: Gravitational force
Gravity is the universal force of attraction acting between all masses. Earth’s gravitational force pulls everything towards its center.
Q28. When you inflate a balloon, the air inside exerts pressure:
• Only on the bottom
• Only on the top
• Equally in all directions
• Only on the sides
Answer: Equally in all directions
Gases, like liquids, exert pressure equally in all directions on the walls of their container.
Q29. Which of the following is an example of force changing the direction of motion?
• A batsman hitting a ball for a six
• A goalkeeper catching a ball
• A potter shaping a clay pot
• A spring being stretched
Answer: A batsman hitting a ball for a six
When the batsman strikes the ball, the force applied changes the direction of the moving ball from its original path.
Q30. The force exerted by a magnet on an iron nail is an example of:
• Electrostatic force
• Gravitational force
• Magnetic force
• Muscular force
Answer: Magnetic force
Magnets exert a force on magnetic materials like iron. This force can be attractive or repulsive and acts without contact.
Q31. What happens to the pressure if the area of contact increases while the force remains the same?
• Pressure increases
• Pressure decreases
• Pressure remains the same
• Pressure becomes zero
Answer: Pressure decreases
Pressure is inversely proportional to area. If the area increases, the pressure decreases for a constant force.
Q32. Our atmosphere exerts pressure on our head. Why are we not crushed by it?
• Because atmospheric pressure is zero
• Because our body exerts equal pressure from inside
• Because our head is very hard
• Because gravity cancels it
Answer: Because our body exerts equal pressure from inside
The fluids inside our body exert an equal and opposite pressure to balance the atmospheric pressure acting from outside.
Q33. Which of the following is an example of a push?
• Drawing a curtain
• Lifting a backpack
• Closing a door
• Plucking a guitar string
Answer: Closing a door
To close a door, you typically push it away from you to make it move.
Q34. The force that acts between two charged bodies is called:
• Magnetic force
• Gravitational force
• Electrostatic force
• Frictional force
Answer: Electrostatic force
Electrostatic force is the force of attraction or repulsion between electrically charged objects.
Q35. Why do tractors have broad tyres?
• To increase pressure on the ground
• To decrease pressure on the ground
• To increase speed
• To look big
Answer: To decrease pressure on the ground
Broad tyres have a larger contact area with the ground, which reduces the pressure exerted by the heavy tractor, preventing it from sinking into soft soil.
Q36. Which of the following forces is always attractive?
• Magnetic force
• Electrostatic force
• Gravitational force
• Frictional force
Answer: Gravitational force
Gravitational force is always attractive. Magnetic and electrostatic forces can be either attractive or repulsive.
Q37. When a spring is stretched, its shape changes. This is due to:
• Frictional force
• Applied force
• Magnetic force
• Electrostatic force
Answer: Applied force
The stretching of a spring occurs because an external force is applied to change its original shape and length.
Q38. The pressure exerted by a gas is due to:
• Its weight
• Its colour
• The particles colliding with the walls
• Its smell
Answer: The particles colliding with the walls
Gas particles are in constant random motion. Pressure is created when these particles collide with the walls of their container.
Q39. Which of the following is not a contact force?
• Friction
• Muscular force
• Mechanical force
• Electrostatic force
Answer: Electrostatic force
Electrostatic force acts without physical contact, unlike friction, muscular, and mechanical forces, which require contact.
Q40. A potter changes the shape of a clay pot by applying force. This is an example of:
• Force changing the speed
• Force changing the state of motion
• Force changing the shape
• Force changing the direction
Answer: Force changing the shape
The potter applies muscular force to mold the soft clay into a desired shape, demonstrating that force can change the shape of an object.
Q41. The force responsible for the falling of raindrops to the ground is:
• Magnetic force
• Electrostatic force
• Gravitational force
• Atmospheric pressure
Answer: Gravitational force
Earth’s gravity pulls the raindrops downwards towards the ground.
Q42. Friction is caused by:
• Smoothness of surfaces
• Irregularities on surfaces
• Colour of surfaces
• Temperature of surfaces
Answer: Irregularities on surfaces
Even apparently smooth surfaces have microscopic irregularities that interlock when in contact, giving rise to friction.
Q43. A ball rolling on the ground stops after some time because of:
• Gravitational force
• Magnetic force
• Frictional force
• Electrostatic force
Answer: Frictional force
The force of friction between the ball and the ground opposes the motion, gradually reducing its speed until it stops.
Q44. Which of the following increases pressure?
• Increasing area with same force
• Decreasing area with same force
• Decreasing force with same area
• Increasing both force and area equally
Answer: Decreasing area with same force
Pressure is inversely proportional to area. Reducing the contact area while keeping the force constant results in higher pressure.
Q45. Which force is used to separate iron pins from a mixture using a magnet?
• Gravitational force
• Muscular force
• Frictional force
• Magnetic force
Answer: Magnetic force
The magnetic force of the magnet attracts the iron pins, pulling them away from the non-magnetic components of the mixture.
Q46. The walls of a dam are made wider at the bottom because:
• Water pressure is less at the bottom
• Water pressure is more at the bottom
• To make it look strong
• To store less water
Answer: Water pressure is more at the bottom
Liquid pressure increases with depth. The bottom of the dam experiences the highest pressure, so the walls are made thicker there to withstand it.
Q47. When a force is applied to a stationary object, it can:
• Only change its shape
• Only change its direction
• Only stop it
• Set it into motion
Answer: Set it into motion
A force can change the state of motion of an object. Applying force to a stationary object can make it start moving.
Q48. Which of the following is an example of electrostatic force?
• A nail sticking to a magnet
• A stone falling to the ground
• Plastic comb attracting paper bits after rubbing
• A boy pushing a bicycle
Answer: Plastic comb attracting paper bits after rubbing
When a plastic comb is rubbed with dry hair, it becomes charged and can attract small pieces of paper due to electrostatic force.
Q49. The weight of an object is the force with which it is pulled towards the Earth. This force is:
• Same everywhere
• Different on different planets
• Always zero
• Not related to gravity
Answer: Different on different planets
Weight depends on the gravitational force of the celestial body. Since gravity varies from planet to planet, weight also varies.
Q50. A person is not able to move a heavy almirah despite pushing it. Which force is preventing the motion?
• Gravitational force
• Electrostatic force
• Frictional force
• Magnetic force
Answer: Frictional force
The force of friction between the almirah and the floor opposes the applied push, and if it is greater than the push, the almirah will not move.