Chapter 4 MCQs

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

1

An object is moving in a straight line at constant speed.

What is the resultant force on the object?

A zero
B equal to its weight
C equal to its mass × speed
D greater than the resistive force

---

2

A book rests on a horizontal table.

Which pair of forces is balanced?

A weight of the book and contact force from the table
B weight of the book and weight of the table
C contact force from the table and friction on the table
D weight of the Earth and contact force from the table

---

3

A box is pulled to the right by a force of 40 N. A frictional force of 15 N acts to the left.

What is the resultant force on the box?

A 15 N to the right
B 25 N to the right
C 40 N to the right
D 55 N to the right

---

4

A trolley has a mass of 6.0 kg. A resultant force of 18 N acts on it.

What is its acceleration?

A 0.33 m/s²
B 3.0 m/s²
C 12 m/s²
D 108 m/s²

---

5

A resultant force of 24 N causes an object to accelerate at 3.0 m/s².

What is the mass of the object?

A 0.125 kg
B 8.0 kg
C 21 kg
D 72 kg

---

6

An object of mass 4.0 kg accelerates at 2.5 m/s².

What is the resultant force acting on it?

A 1.6 N
B 6.5 N
C 10 N
D 16 N

---

7

A car is travelling at constant velocity on a level road.

Which statement is correct?

A The driving force is greater than the resistive force.
B The resistive force is greater than the driving force.
C The driving force equals the resistive force.
D There are no forces acting on the car.

---

8

A lift moves upwards at constant speed.

Which statement is correct?

A tension is greater than weight
B tension is equal to weight
C weight is greater than tension
D resultant force is upwards

---

9

A lift accelerates upwards.

Which statement is correct?

A tension is greater than weight
B tension is equal to weight
C weight is greater than tension
D resultant force is zero

---

10

A lift accelerates downwards.

Which statement is correct?

A tension is greater than weight
B tension is equal to weight
C weight is greater than tension
D there is no weight acting on the lift

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

11

A student pushes a box along the floor at constant speed.

Which statement is correct?

A The pushing force is greater than friction.
B The pushing force is equal to friction.
C Friction is greater than the pushing force.
D The resultant force acts in the direction of motion.

---

12

A 2.0 kg object is acted on by a resultant force of 5.0 N.

What is its acceleration?

A 0.40 m/s²
B 2.5 m/s²
C 7.0 m/s²
D 10 m/s²

---

13

An object has mass 10 kg. Forces of 60 N and 20 N act on it in opposite directions.

What is the acceleration of the object?

A 2.0 m/s²
B 4.0 m/s²
C 6.0 m/s²
D 8.0 m/s²

---

14

Two horizontal forces act on a crate. 35 N acts east and 55 N acts west.

What is the resultant force?

A 20 N east
B 20 N west
C 90 N east
D 90 N west

---

15

Three forces act along the same straight line on an object.

• 12 N to the right

• 7 N to the left

• 4 N to the right

What is the resultant force?

A 1 N to the right
B 9 N to the right
C 15 N to the right
D 23 N to the right

---

16

A box has two forces acting on it: 50 N to the right and 50 N to the left.

Which statement is correct?

A The box must be at rest.
B The box must be moving at constant speed.
C The box must have zero acceleration.
D The box must be speeding up.

---

17

A resultant force acts on an object.

Which change must occur?

A mass changes
B velocity changes
C weight becomes zero
D density changes

---

18

A force acts on a moving object at right angles to its direction of motion.

Which quantity can change?

A mass only
B speed only
C direction of motion
D volume only

---

19

Which statement is Newton’s first law?

A Force equals mass × acceleration.
B Every action has an equal and opposite reaction.
C An object remains at rest or in uniform motion unless acted on by a resultant force.
D Momentum before a collision equals momentum after a collision.

---

20

Which situation shows Newton’s first law most clearly?

A A ball speeds up when kicked.
B A moving puck continues moving in a straight line on a nearly frictionless surface.
C A spring stretches when loaded.
D A rocket pushes gases backwards.

---

21

A student says, “If an object is moving, there must be a resultant force acting on it.”

Why is this wrong?

A Moving objects never have forces on them.
B A moving object can continue at constant velocity with zero resultant force.
C Resultant force only acts on stationary objects.
D Forces only change mass.

---

22

A parachutist is falling at constant velocity.

What is the resultant force on the parachutist?

A zero
B equal to weight downwards
C equal to air resistance upwards
D greater than weight

---

23

A ball is falling through air and speeding up.

Which statement is correct?

A weight is greater than air resistance
B air resistance is greater than weight
C weight is equal to air resistance
D no forces act on the ball

---

24

An object is thrown upwards. Ignore air resistance.

Which force acts on the object after it leaves the hand?

A upward force from the hand only
B weight only
C weight and upward force from the hand
D no force

---

25

A toy car is pushed and then released on a rough horizontal surface. It slows down.

Which force causes it to slow down?

A weight
B normal contact force
C friction
D gravitational field strength

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

26

Which force is a contact force?

A gravitational force
B magnetic force
C electrostatic force
D friction

---

27

Which force is a non-contact force?

A friction
B tension
C normal contact force
D magnetic force

---

28

A metal ball is attracted by a magnet.

Which force acts on the metal ball?

A electrostatic force
B magnetic force
C frictional force
D tension

---

29

A charged plastic rod attracts small pieces of paper.

Which force acts on the paper?

A electrostatic force
B gravitational force only
C magnetic force
D tension

---

30

A rope pulls a box.

What is the force in the rope called?

A tension
B weight
C drag
D contact force only

---

31

Which force always acts vertically downwards near the Earth’s surface?

A tension
B weight
C friction
D thrust

---

32

A plane moves forward because its engines provide a force.

What is this force called?

A weight
B friction
C thrust
D normal reaction

---

33

A ball rests on a horizontal surface.

Which free-body diagram description is correct?

A weight downwards only
B contact force upwards only
C weight downwards and contact force upwards, equal in size
D weight upwards and contact force downwards, equal in size

---

34

A box is pulled across a rough horizontal floor at constant speed.

Which forces should appear on a free-body diagram of the box?

A weight only
B weight, normal contact force, pulling force and friction
C pulling force and friction only
D weight, normal contact force and pulling force only

---

35

A stone hangs motionless from a string.

Which forces act on the stone?

A weight only
B tension only
C weight and tension
D weight, tension and contact force from air only

---

36

A stone hangs motionless from a string.

What is the relationship between the tension and the weight?

A tension is greater than weight
B tension is equal to weight
C tension is less than weight
D tension is zero

---

37

A box is on a slope and remains at rest.

Which force prevents it sliding down the slope?

A weight
B friction
C thrust
D magnetic force

---

38

A box on a slope remains at rest.

Which statement about the forces is correct?

A The resultant force on the box is zero.
B The weight of the box is zero.
C Friction must be greater than the component of weight down the slope.
D The normal contact force acts vertically upwards.

---

39

Two students push a trolley in opposite directions. Student X pushes with 90 N east. Student Y pushes with 130 N west. The trolley has mass 20 kg.

What is the acceleration of the trolley?

A 2.0 m/s² east
B 2.0 m/s² west
C 11 m/s² east
D 11 m/s² west

---

40

A 5.0 kg object has an acceleration of 4.0 m/s² to the left.

What is the resultant force?

A 1.25 N left
B 9.0 N left
C 20 N left
D 20 N right

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

41

Newton’s third law states that when object A exerts a force on object B, object B exerts a force on object A.

Which statement about the two forces is correct?

A They act on the same object.
B They act in the same direction.
C They are equal in size and opposite in direction.
D They are different types of force.

---

42

A book rests on a table.

Which pair of forces is a Newton’s third law pair?

A weight of book and contact force on book from table
B gravitational force of Earth on book and gravitational force of book on Earth
C contact force on book from table and weight of book
D friction on book and weight of table

---

43

A swimmer pushes water backwards.

According to Newton’s third law, what happens?

A The water pushes the swimmer forwards.
B The swimmer has no resultant force.
C The water pulls the swimmer backwards.
D The swimmer’s weight decreases.

---

44

A rocket moves upwards because it pushes gases downwards.

Which force is the Newton’s third law pair to the force of the rocket on the gases?

A weight of rocket
B force of gases on rocket
C air resistance on rocket
D gravitational force of Earth on rocket

---

45

A student says, “Newton’s third law forces cancel each other, so motion cannot happen.”

Why is this wrong?

A The forces act on different objects.
B The forces act in the same direction.
C The forces are not equal.
D One of the forces is always zero.

---

46

A person stands still on the floor.

Which pair is not a Newton’s third law pair?

A force of Earth on person and force of person on Earth
B force of floor on person and force of person on floor
C weight of person and normal contact force on person
D gravitational force on person by Earth and gravitational force on Earth by person

---

47

A bat hits a ball.

Which statement is correct?

A The bat exerts a larger force on the ball than the ball exerts on the bat.
B The ball exerts a larger force on the bat than the bat exerts on the ball.
C The forces are equal in size and opposite in direction.
D The force on the ball acts before the force on the bat.

---

48

A car of mass 1200 kg has a resultant force of 3000 N forwards.

What is the acceleration of the car?

A 0.40 m/s²
B 2.5 m/s²
C 3.6 m/s²
D 4.0 m/s²

---

49

A trolley of mass 2.5 kg is pulled by a force of 12 N. A resistive force of 4.5 N acts in the opposite direction.

What is the acceleration of the trolley?

A 1.8 m/s²
B 3.0 m/s²
C 4.8 m/s²
D 6.6 m/s²

---

50

An object is acted on by forces of 10 N north, 15 N south, 8 N north and 3 N south.

What is the resultant force?

A 0 N
B 3 N north
C 6 N north
D 6 N south

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Answer Key

Q	Ans	Q	Ans	Q	Ans	Q	Ans	Q	Ans
1	A	11	B	21	B	31	B	41	C
2	A	12	B	22	A	32	C	42	B
3	B	13	B	23	A	33	C	43	A
4	B	14	B	24	B	34	B	44	B
5	B	15	B	25	C	35	C	45	A
6	C	16	C	26	D	36	B	46	C
7	C	17	B	27	D	37	B	47	C
8	B	18	C	28	B	38	A	48	B
9	A	19	C	29	A	39	B	49	B
10	C	20	B	30	A	40	C	50	A

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

Detailed Explanations

1. A

• Constant speed in a straight line means constant velocity.

• If velocity is constant, acceleration is zero.

• Resultant force = mass × acceleration.

• Resultant force = 0.

• So the resultant force is zero.

2. A

• The book is at rest, so resultant force on the book is zero.

• Weight acts downwards.

• Contact force from the table acts upwards.

• These two forces are equal and opposite, acting on the same object.

• So they are balanced forces.

3. B

• Force to the right = 40 N.

• Friction to the left = 15 N.

• Resultant force = 40 − 15 = 25 N to the right.

• Do not add forces acting in opposite directions.

4. B

• F = ma.

• a = F / m.

• a = 18 / 6.0.

• a = 3.0 m/s².

5. B

• F = ma.

• m = F / a.

• m = 24 / 3.0.

• m = 8.0 kg.

6. C

• F = ma.

• F = 4.0 × 2.5.

• F = 10 N.

7. C

• Constant velocity means zero acceleration.

• Zero acceleration means zero resultant force.

• Therefore driving force = resistive force.

• The car is moving, but the forces are still balanced. That is the trap.

8. B

• The lift moves upwards at constant speed.

• Constant speed means acceleration is zero.

• Resultant force is zero.

• Therefore tension = weight.

9. A

• The lift accelerates upwards.

• Resultant force must be upwards.

• So upward tension must be greater than downward weight.

• Therefore tension > weight.

10. C

• The lift accelerates downwards.

• Resultant force must be downwards.

• So downward weight must be greater than upward tension.

• Therefore weight > tension.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

11. B

• The box moves at constant speed.

• Constant speed means resultant force = 0.

• So pushing force = frictional force.

• If pushing force were greater, the box would accelerate.

12. B

• a = F / m.

• a = 5.0 / 2.0.

• a = 2.5 m/s².

13. B

• Forces are opposite.

• Resultant force = 60 − 20 = 40 N.

• a = F / m.

• a = 40 / 10.

• a = 4.0 m/s².

14. B

• Forces:

  • 35 N east

  • 55 N west

• Resultant = 55 − 35 = 20 N west.

• Direction is towards the larger force.

15. B

• Right forces = 12 + 4 = 16 N.

• Left force = 7 N.

• Resultant = 16 − 7 = 9 N to the right.

16. C

• 50 N right and 50 N left cancel.

• Resultant force = 0.

• Therefore acceleration = 0.

• The box may be at rest or moving at constant velocity.

• The only thing that must be true is zero acceleration.

17. B

• A resultant force causes acceleration.

• Acceleration means change in velocity.

• The object may change speed, direction, or both.

• Mass, weight and density do not have to change.

18. C

• A force at right angles to motion changes the direction of motion.

• This happens in circular motion.

• The speed may stay constant, but velocity changes because direction changes.

19. C

• Newton’s first law:

• An object remains at rest or continues moving in a straight line at constant speed unless acted on by a resultant force.

• A is Newton’s second law.

• B is Newton’s third law.

20. B

• A puck moving on a nearly frictionless surface continues in a straight line.

• This shows that motion does not need a continuous resultant force.

• It only needs a resultant force to change the motion.

---

21. B

• An object can move with constant velocity even when resultant force is zero.

• Resultant force is only needed to change velocity.

• “Moving” does not automatically mean “resultant force acting.”

• That misconception is MCQ poison.

22. A

• Falling at constant velocity means acceleration is zero.

• If acceleration is zero, resultant force is zero.

• Weight downwards = air resistance upwards.

• This is terminal velocity.

23. A

• The ball is speeding up downwards.

• So resultant force is downwards.

• Weight acts downwards.

• Air resistance acts upwards.

• Therefore weight > air resistance.

24. B

• After the object leaves the hand, the hand no longer pushes it.

• Ignoring air resistance, only weight acts.

• Weight acts downwards throughout the motion, even when the object is moving upwards.

25. C

• The toy car slows down because friction acts opposite to its motion.

• Weight and normal contact force act vertically, so they do not directly slow horizontal motion.

• Friction transfers kinetic energy to thermal energy.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

26. D

• Friction is a contact force.

• It acts when surfaces interact.

• Gravitational, magnetic and electrostatic forces can act without physical contact.

27. D

• Magnetic force is a non-contact force.

• It can act through space without touching.

• Friction, tension and normal contact force require contact.

28. B

• A magnet attracts the metal ball using magnetic force.

• Electrostatic force involves charges.

• Tension needs a string or rope.

• Friction needs surfaces rubbing/sliding.

29. A

• A charged rod attracts paper by electrostatic force.

• This happens due to charges and induced charge separation.

• It is not magnetic unless magnetic materials/magnets are involved.

30. A

• The pulling force in a rope/string is called tension.

• Tension acts along the rope.

• It pulls objects, not pushes them.

31. B

• Weight is the gravitational force on an object.

• Near Earth’s surface, it acts vertically downwards.

• Tension, friction and thrust can act in different directions depending on the situation.

32. C

• The forward force from engines is thrust.

• Thrust drives the plane forward.

• Weight acts downward.

• Friction/drag usually opposes motion.

33. C

• A ball resting on a horizontal surface has:

  • weight downwards

  • normal contact force upwards

• Since it is at rest, these forces are equal in size.

• Resultant force is zero.

34. B

• A box pulled across a rough floor has:

  • weight downward

  • normal contact force upward

  • pulling force forward

  • friction backward

• Since it moves at constant speed, horizontal forces are balanced.

35. C

• The hanging stone has:

  • weight downward

  • tension upward

• It is motionless, so these forces are equal.

• There is no normal contact force because it is not resting on a surface.

---

36. B

• The stone is motionless.

• Resultant force = 0.

• Therefore tension = weight.

• If tension were greater, the stone would accelerate upwards.

• If weight were greater, it would accelerate downwards.

37. B

• A box on a slope tends to slide down due to a component of weight.

• Friction acts up the slope to oppose sliding.

• So friction prevents it from sliding.

38. A

• The box remains at rest.

• Therefore acceleration = 0.

• Therefore resultant force = 0.

• Friction is equal to the component of weight down the slope, not greater.

• Normal contact force acts perpendicular to the slope, not vertically upward.

39. B

• Force east = 90 N.

• Force west = 130 N.

• Resultant = 130 − 90 = 40 N west.

• a = F / m.

• a = 40 / 20 = 2.0 m/s² west.

40. C

• F = ma.

• F = 5.0 × 4.0.

• F = 20 N.

• Direction of force is the same as acceleration.

• So resultant force = 20 N left.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

41. C

• Newton’s third law forces are:

  • equal in size

  • opposite in direction

  • same type of force

  • acting on different objects

• They do not act on the same object.

42. B

• The Earth pulls the book down.

• The book pulls the Earth up with an equal gravitational force.

• These two forces act on different objects.

• Therefore this is a Newton’s third law pair.

43. A

• The swimmer pushes water backwards.

• The water pushes the swimmer forwards.

• These forces are equal and opposite.

• This is Newton’s third law in action.

44. B

• The rocket pushes gases downwards.

• The gases push the rocket upwards.

• This upward force from gases on the rocket is the third-law pair.

• Weight and air resistance are separate forces on the rocket.

45. A

• Newton’s third law forces do not cancel each other because they act on different objects.

• Forces only cancel when they act on the same object in opposite directions.

• Rocket motion, walking and swimming all work because of this.

46. C

• Weight of person and normal contact force on person both act on the same object: the person.

• They are balanced forces, not a Newton’s third law pair.

• A, B and D are third-law pairs because each force acts on a different object.

47. C

• When the bat hits the ball:

  • bat exerts force on ball

  • ball exerts force on bat

• These forces are equal in size and opposite in direction.

• They occur at the same time.

• The ball accelerates more because it has smaller mass, not because the force is larger.

48. B

• a = F / m.

• a = 3000 / 1200.

• a = 2.5 m/s².

49. B

• Pulling force = 12 N.

• Resistive force = 4.5 N.

• Resultant force = 12 − 4.5 = 7.5 N.

• a = F / m.

• a = 7.5 / 2.5.

• a = 3.0 m/s².

50. A

• North forces = 10 + 8 = 18 N.

• South forces = 15 + 3 = 18 N.

• Resultant force = 18 − 18 = 0 N.

• Forces are balanced.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

Common Traps From This Chapter

Trap	Correct Rule
Moving object must have resultant force	false; constant velocity means zero resultant force
Constant speed in straight line	resultant force = 0
Acceleration	resultant force is not zero
F = ma	resultant force = mass × acceleration
Opposite forces	subtract smaller from larger
Same direction forces	add
Balanced forces	same object, equal and opposite
Newton’s third law pair	different objects, equal and opposite
Third-law forces cancel	false, because they act on different objects
Weight and normal contact force	balanced pair, not third-law pair
Terminal velocity	weight = air resistance
Falling and speeding up	weight > air resistance
Object thrown up after release	only weight acts if air resistance ignored
Tension in motionless hanging object	tension = weight
Lift moving at constant speed	tension = weight
Lift accelerating upwards	tension > weight
Lift accelerating downwards	weight > tension
Force at right angles to motion	changes direction of motion
Friction	contact force opposing motion/sliding
Magnetic/electrostatic/gravitational	non-contact forces