Class 9 Science Chapter 6 | MCQ

NCERT Class 9 Science MCQ | Chapter 6: How Forces Affect Motion

Q1. A force can change the:
(A) State of motion of an object
(B) Shape of an object
(C) Direction of motion of an object
(D) All of the above
Answer: (D) All of the above

Q2. The SI unit of force is:
(A) Joule
(B) Newton
(C) Pascal
(D) Watt
Answer: (B) Newton

Q3. The symbol for the SI unit of force is:
(A) n
(B) F
(C) N
(D) Ne
Answer: (C) N

Q4. Force is a physical quantity for which we need to specify:
(A) Only magnitude
(B) Only direction
(C) Magnitude and direction
(D) Only unit
Answer: (C) Magnitude and direction

Q5. The magnitude of a force expresses its:
(A) Direction
(B) Strength
(C) Mass
(D) Acceleration
Answer: (B) Strength

Q6. A spring balance can be used to measure:
(A) Mass only
(B) Time
(C) Force
(D) Velocity
Answer: (C) Force

Q7. Two forces acting on an object are balanced when they are:
(A) Equal in magnitude and in the same direction
(B) Unequal in magnitude and opposite in direction
(C) Equal in magnitude and opposite in direction
(D) Zero in magnitude
Answer: (C) Equal in magnitude and opposite in direction

Q8. When balanced forces act on an object, the net force is:
(A) Maximum
(B) Zero
(C) Negative
(D) Infinite
Answer: (B) Zero

Q9. When forces acting on an object are not balanced, the net force is:
(A) Always zero
(B) Non-zero
(C) Always equal to friction
(D) Always equal to weight
Answer: (B) Non-zero

Q10. Two forces of 10 N and 6 N act in the same direction on a block. The net force is:
(A) 4 N
(B) 6 N
(C) 10 N
(D) 16 N
Answer: (D) 16 N

Q11. Two opposite forces of 10 N and 6 N act on a block, with the 10 N force towards the right. The net force is:
(A) 4 N towards the left
(B) 4 N towards the right
(C) 16 N towards the right
(D) 16 N towards the left
Answer: (B) 4 N towards the right

Q12. Two opposite forces of 6 N and 10 N act on a block, with the 10 N force towards the left. The net force is:
(A) 4 N towards the left
(B) 4 N towards the right
(C) 16 N towards the left
(D) 16 N towards the right
Answer: (A) 4 N towards the left

Q13. The force of friction generally acts:
(A) In the direction of motion
(B) Opposite to the direction of motion
(C) Vertically upward
(D) Vertically downward
Answer: (B) Opposite to the direction of motion

Q14. A box starts moving when the applied force becomes:
(A) Smaller than friction
(B) Equal to zero
(C) Larger than friction
(D) Equal to its weight
Answer: (C) Larger than friction

Q15. The normal force exerted by a surface acts:
(A) Downwards
(B) Upwards, perpendicular to the surface
(C) Along the direction of motion
(D) Opposite to gravity horizontally
Answer: (B) Upwards, perpendicular to the surface

Q16. The gravitational force acting on an object near Earth’s surface acts:
(A) Upwards
(B) Horizontally
(C) Downwards
(D) Along the direction of motion
Answer: (C) Downwards

Q17. If the force of friction acting on a moving object is smaller, the object:
(A) Stops immediately
(B) Loses velocity more slowly
(C) Loses velocity more quickly
(D) Has zero acceleration always
Answer: (B) Loses velocity more slowly

Q18. According to the chapter, a smaller spring balance reading indicates:
(A) Larger friction
(B) Smaller friction
(C) Zero mass
(D) Larger acceleration
Answer: (B) Smaller friction

Q19. Galileo argued that if all impediments to motion are removed, a body moving along a horizontal plane will:
(A) Stop immediately
(B) Continue moving indefinitely
(C) Move in a circle
(D) Fall vertically
Answer: (B) Continue moving indefinitely

Q20. Newton used the term “inertia” to describe the tendency of an object to:
(A) Increase its mass
(B) Resist change in its state of rest or uniform motion
(C) Increase its speed automatically
(D) Change its shape
Answer: (B) Resist change in its state of rest or uniform motion

Q21. Newton’s first law of motion states that an object at rest remains at rest unless:
(A) Its mass changes
(B) A net force acts upon it
(C) Its temperature changes
(D) Its volume changes
Answer: (B) A net force acts upon it

Q22. According to Newton’s first law, an object in motion continues to move with:
(A) Increasing velocity
(B) Decreasing velocity
(C) Constant velocity, unless a net force acts
(D) Zero velocity
Answer: (C) Constant velocity, unless a net force acts

Q23. If the net force acting on an object is zero, its acceleration is:
(A) Zero
(B) Maximum
(C) Negative
(D) Infinite
Answer: (A) Zero

Q24. An object moving with constant velocity has:
(A) A non-zero net force
(B) Zero net force
(C) Increasing net force
(D) Decreasing mass
Answer: (B) Zero net force

Q25. If a moving box is pushed forward with a force equal to the frictional force acting backward, the box will:
(A) Stop immediately
(B) Accelerate forward
(C) Continue moving with constant velocity
(D) Move backward
Answer: (C) Continue moving with constant velocity

Q26. If no net force acts on an object initially at rest, the object:
(A) Starts moving
(B) Remains at rest
(C) Accelerates
(D) Moves with increasing velocity
Answer: (B) Remains at rest

Q27. Newton’s second law relates force with:
(A) Mass and acceleration
(B) Distance and time
(C) Density and volume
(D) Pressure and area
Answer: (A) Mass and acceleration

Q28. According to Newton’s second law, acceleration is directly proportional to:
(A) Mass
(B) Net force
(C) Time
(D) Density
Answer: (B) Net force

Q29. For a given force, acceleration is inversely proportional to:
(A) Force
(B) Velocity
(C) Mass
(D) Time
Answer: (C) Mass

Q30. The mathematical expression of Newton’s second law is:
(A) F = m/a
(B) F = ma
(C) F = a/m
(D) F = m + a
Answer: (B) F = ma

Q31. If the force acting on an object is doubled while its mass remains constant, its acceleration:
(A) Becomes half
(B) Remains the same
(C) Doubles
(D) Becomes zero
Answer: (C) Doubles

Q32. If the mass of an object is doubled while the force remains constant, its acceleration:
(A) Doubles
(B) Becomes half
(C) Becomes four times
(D) Remains the same
Answer: (B) Becomes half

Q33. One newton is the force that produces an acceleration of:
(A) 1 m/s on a 1 kg object
(B) 1 m/s² on a 1 kg object
(C) 1 m/s² on a 10 kg object
(D) 10 m/s² on a 1 kg object
Answer: (B) 1 m/s² on a 1 kg object

Q34. The SI unit of acceleration is:
(A) m/s
(B) m/s²
(C) kg m/s
(D) N/m
Answer: (B) m/s²

Q35. The gravitational force acting on an object of mass m is given by:
(A) F = ma
(B) F = m/v
(C) F = mg
(D) F = m + g
Answer: (C) F = mg

Q36. The value of acceleration due to gravitational force near the surface of Earth is approximately:
(A) 2.8 m/s²
(B) 5.8 m/s²
(C) 9.8 m/s²
(D) 15.8 m/s²
Answer: (C) 9.8 m/s²

Q37. For quick estimations, the value of g can be taken as:
(A) 5 m/s²
(B) 8 m/s²
(C) 9 m/s²
(D) 10 m/s²
Answer: (D) 10 m/s²

Q38. Momentum of an object is defined as the product of:
(A) Mass and acceleration
(B) Mass and velocity
(C) Force and time
(D) Force and acceleration
Answer: (B) Mass and velocity

Q39. The direction of momentum is the same as the direction of:
(A) Force
(B) Acceleration
(C) Velocity
(D) Mass
Answer: (C) Velocity

Q40. A fast-moving cricket ball is caught by gradually pulling the hands backward. This increases the:
(A) Mass of the ball
(B) Time over which the velocity changes
(C) Velocity of the ball
(D) Weight of the ball
Answer: (B) Time over which the velocity changes

Q41. Airbags in vehicles help reduce the force on a passenger during a collision by:
(A) Decreasing the collision time
(B) Increasing the time over which the collision occurs
(C) Increasing the mass of the passenger
(D) Increasing the velocity
Answer: (B) Increasing the time over which the collision occurs

Q42. A coconut hitting the ground stops in a very short time. The ground therefore exerts:
(A) A very small force
(B) No force
(C) A very large force
(D) Only frictional force
Answer: (C) A very large force

Q43. Newton’s third law states that whenever one object exerts a force on another object, the second object:
(A) Exerts no force
(B) Exerts an equal and opposite force
(C) Exerts a smaller force
(D) Exerts a force in the same direction
Answer: (B) Exerts an equal and opposite force

Q44. The action and reaction forces in Newton’s third law act on:
(A) The same object
(B) Two different objects
(C) Three objects
(D) No objects
Answer: (B) Two different objects

Q45. When a person pushes a table, the table pushes the person:
(A) In the same direction
(B) In the opposite direction
(C) Vertically downward
(D) With zero force
Answer: (B) In the opposite direction

Q46. While walking, a person pushes the ground:
(A) Forward
(B) Backward
(C) Upward only
(D) Sideways only
Answer: (B) Backward

Q47. While walking, the ground exerts a frictional force on the person’s feet:
(A) Backward
(B) Forward
(C) Downward
(D) Zero
Answer: (B) Forward

Q48. A rocket moves upward because:
(A) It pushes the exhaust gases upward
(B) The exhaust gases are expelled downward and exert an equal and opposite force on the rocket
(C) Gravity pushes it upward
(D) There is no force acting on it
Answer: (B) The exhaust gases are expelled downward and exert an equal and opposite force on the rocket

Q49. A canoe moves forward when the canoeist:
(A) Pushes water forward
(B) Pushes water backward with the paddle
(C) Stops using the paddle
(D) Pulls the water upward
Answer: (B) Pushes water backward with the paddle

Q50. One hundred oarsmen are rowing a boat. Ninety-five apply 200 N each in the direction that propels the boat forward, while five apply 200 N in the opposite direction. What is the net force on the boat?
(A) 18,000 N
(B) 19,000 N
(C) 20,000 N
(D) 10,000 N
Answer: (B) 18,000 N

NCERT Class 9 Science MCQ | Chapter 6: How Forces Affect Motion

Assertion Reason Type Question

ASSERTION–REASON QUESTIONS

Q1. Assertion (A): An object continues to remain at rest if the net force acting on it is zero.

Reason (R): According to Newton’s first law of motion, an object at rest remains at rest unless a net force acts upon it.