Force and Laws of Motion Part 4: MCQs (Q76–Q100)

⚡ Force and Laws of Motion – Class 9 Science MCQs

Section 4: Numericals & HOTS (Q76–Q100)

Q76. A body of mass 10 kg has acceleration 2 m/s². Force acting = ?

A. 5 N
B. 10 N
C. 15 N
D. 20 N

✅ Correct Answer: D. 20 N

Explanation:

$F=ma=10×2=20 NF = ma = 10 × 2 = 20 \, N$ .
Others are incorrect values.

Q77. Momentum of a body of mass 5 kg moving with 3 m/s = ?

A. 8 kg m/s
B. 10 kg m/s
C. 12 kg m/s
D. 15 kg m/s

✅ Correct Answer: C. 15 kg m/s

Explanation:

$p=mv=5×3=15 kg m/sp = mv = 5 × 3 = 15 \, kg \, m/s$ .

Q78. A 1000 kg car moving with velocity 36 km/h. Momentum = ?

A. 10000 kg m/s
B. 20000 kg m/s
C. 30000 kg m/s
D. 36000 kg m/s

✅ Correct Answer: A. 10000 kg m/s

Explanation:

Convert velocity: $36 km/h=10 m/s36 \, km/h = 10 \, m/s$ .
Momentum = $1000\times10=100001000 \times 10 = 10000$ .

Q79. A bullet of mass 0.05 kg moving at 200 m/s. Momentum = ?

A. 5 kg m/s
B. 10 kg m/s
C. 15 kg m/s
D. 20 kg m/s

✅ Correct Answer: B. 10 kg m/s

Explanation:

$p=mv=0.05\times200=10p = mv = 0.05 \times 200 = 10$ .

Q80. A 5 kg object is accelerated from rest to 20 m/s in 4 s. Force applied = ?

A. 20 N
B. 25 N
C. 30 N
D. 40 N

✅ Correct Answer: B. 25 N

Explanation:

$a=Δv/t=20/4=5a = Δv/t = 20/4 = 5$ .
$F=ma=5\times5=25NF = ma = 5 \times 5 = 25 N$ .

Q81. A force of 50 N acts on 10 kg body. Acceleration produced = ?

A. 2 m/s²
B. 5 m/s²
C. 10 m/s²
D. 50 m/s²

✅ Correct Answer: B. 5 m/s²

Explanation:

$a=F/m=50/10=5a = F/m = 50/10 = 5$ .

Q82. A hammer of mass 1 kg strikes a nail with velocity 10 m/s. Momentum delivered = ?

A. 1 kg m/s
B. 5 kg m/s
C. 10 kg m/s
D. 15 kg m/s

✅ Correct Answer: C. 10 kg m/s

Explanation:

$p=mv=1\times10=10p = mv = 1 \times 10 = 10$ .

Q83. A gun of mass 5 kg fires a bullet of mass 50 g at velocity 100 m/s. Recoil velocity of gun = ?

A. –1 m/s
B. –2 m/s
C. –0.5 m/s
D. –5 m/s

✅ Correct Answer: A. –1 m/s

Explanation:

Bullet momentum = $0.05\times100=50.05 \times 100 = 5$ .
Gun momentum = –5.
$vgun=–5/5=–1 m/sv_{gun} = –5/5 = –1 \, m/s$ .

Q84. A force produces an acceleration of 4 m/s² in mass 3 kg. Find force.

A. 8 N
B. 10 N
C. 12 N
D. 15 N

✅ Correct Answer: C. 12 N

Explanation:

$F=ma=3\times4=12F = ma = 3 \times 4 = 12$ .

Q85. Which factor does not affect momentum?

A. Mass
B. Velocity
C. Acceleration
D. Both A and B

✅ Correct Answer: C. Acceleration

Explanation:

Momentum = mass × velocity.

Q86. A 50 g bullet moving with 400 m/s hits wooden block of 1 kg. Total momentum before hit = ?

A. 10 kg m/s
B. 15 kg m/s
C. 20 kg m/s
D. 25 kg m/s

✅ Correct Answer: C. 20 kg m/s

Explanation:

Bullet mass = 0.05 kg.
Momentum = 0.05 × 400 = 20.

Q87. If net external force is zero, momentum of system:

A. Increases
B. Decreases
C. Remains constant
D. Becomes zero

✅ Correct Answer: C. Remains constant

Q88. An object of mass 2 kg moving with 5 m/s. Kinetic energy = ?

A. 25 J
B. 10 J
C. 20 J
D. 50 J

✅ Correct Answer: A. 25 J

Explanation:

$KE=½mv2=½\times2\times25=25JKE = ½ mv^2 = ½ \times 2 \times 25 = 25 J$ .

Q89. If acceleration is doubled, force becomes:

A. Half
B. Same
C. Double
D. Four times

✅ Correct Answer: C. Double

Explanation:

$F=maF = ma$ . Force ∝ acceleration.

Q90. A ball of mass 2 kg moving at 3 m/s is stopped by a force in 0.5 s. Force applied = ?

A. 6 N
B. 9 N
C. 12 N
D. 15 N

✅ Correct Answer: C. 12 N

Explanation:

Initial momentum = 6, final = 0.
Δp = 6, time = 0.5 → F = 6/0.5 = 12 N.

Q91. Which is true about action-reaction forces?

A. Act on same body
B. Always cancel out
C. Act on different bodies
D. Unequal

✅ Correct Answer: C. Act on different bodies

Q92. A boy pushes wall with 10 N. Wall pushes back with:

A. 0 N
B. 5 N
C. 10 N
D. Cannot say

✅ Correct Answer: C. 10 N

Q93. A car of mass 1500 kg moving with velocity 15 m/s. Momentum = ?

A. 1500 kg m/s
B. 22500 kg m/s
C. 20000 kg m/s
D. 25000 kg m/s

✅ Correct Answer: B. 22500 kg m/s

Explanation:

$p=m\timesv=1500\times15=22500p = m \times v = 1500 \times 15 = 22500$ .

Q94. Why are airbags used in cars?

A. Increase speed
B. Decrease speed
C. Increase time of impact
D. Reduce car weight

✅ Correct Answer: C. Increase time of impact

Explanation:

More time → less force on passengers.

Q95. A man jumps off a boat. Boat moves backward because:

A. Inertia
B. Newton’s first law
C. Newton’s third law
D. Gravity

✅ Correct Answer: C. Newton’s third law

Q96. A force of 10 N acts on 2 kg object for 3 s. Change in momentum = ?

A. 10 kg m/s
B. 20 kg m/s
C. 30 kg m/s
D. 40 kg m/s

✅ Correct Answer: C. 30 kg m/s

Explanation:

Impulse = F × t = 10 × 3 = 30.

Q97. Force required to stop 1000 kg car moving with 10 m/s in 5 s = ?

A. 1000 N
B. 2000 N
C. 2500 N
D. 3000 N

✅ Correct Answer: A. 1000 N

Explanation:

Initial momentum = 10000, final = 0.
Δp = 10000, t = 5 → F = 2000 N.
Correction: Actually 10000/5 = 2000 N.
✅ Correct Answer = B. 2000 N

Q98. A bullet of mass 0.02 kg moving with 300 m/s hits wall, comes to rest in 0.01 s. Force = ?

A. 200 N
B. 300 N
C. 400 N
D. 600 N

✅ Correct Answer: D. 600 N

Explanation:

Δp = mv = 0.02 × 300 = 6.
F = Δp/Δt = 6/0.01 = 600.

Q99. A 2 kg object moving at 4 m/s has same momentum as:

A. 4 kg object at 2 m/s
B. 1 kg object at 2 m/s
C. 0.5 kg object at 8 m/s
D. Both A and C

✅ Correct Answer: D. Both A and C

Explanation:

Momentum = 8 kg m/s. Options A & C also give 8.

Q100. Conservation of momentum is applicable when:

A. Net external force = 0
B. Mass = constant
C. Velocity = constant
D. Acceleration = zero

✅ Correct Answer: A. Net external force = 0

Explanation:

Momentum is conserved in isolated systems (no external force).

Force and Laws of Motion Class 9, CBSE Class 9 Science MCQs, NCERT Class 9 motion questions, Class 9 Science exam practice, Online learning Science Class 9, force and laws of motion class 9 mcqs with answers, cbse class 9 science force and laws of motion multiple choice questions, ncert class 9 force and laws of motion quiz online, important mcqs for cbse class 9 science motion chapter, force and laws of motion class 9 mcqs for online learning

Force and Laws of Motion Part 4: MCQs (Q76–Q100)

⚡ Force and Laws of Motion – Class 9 Science MCQs

Section 4: Numericals & HOTS (Q76–Q100)

Q76. A body of mass 10 kg has acceleration 2 m/s². Force acting = ?

Q77. Momentum of a body of mass 5 kg moving with 3 m/s = ?

Q78. A 1000 kg car moving with velocity 36 km/h. Momentum = ?

Q79. A bullet of mass 0.05 kg moving at 200 m/s. Momentum = ?

Q80. A 5 kg object is accelerated from rest to 20 m/s in 4 s. Force applied = ?

Q81. A force of 50 N acts on 10 kg body. Acceleration produced = ?

Q82. A hammer of mass 1 kg strikes a nail with velocity 10 m/s. Momentum delivered = ?

Q83. A gun of mass 5 kg fires a bullet of mass 50 g at velocity 100 m/s. Recoil velocity of gun = ?

Q84. A force produces an acceleration of 4 m/s² in mass 3 kg. Find force.

Q85. Which factor does not affect momentum?

Q86. A 50 g bullet moving with 400 m/s hits wooden block of 1 kg. Total momentum before hit = ?

Q87. If net external force is zero, momentum of system:

Q88. An object of mass 2 kg moving with 5 m/s. Kinetic energy = ?

Q89. If acceleration is doubled, force becomes:

Q90. A ball of mass 2 kg moving at 3 m/s is stopped by a force in 0.5 s. Force applied = ?

Q91. Which is true about action-reaction forces?

Q92. A boy pushes wall with 10 N. Wall pushes back with:

Q93. A car of mass 1500 kg moving with velocity 15 m/s. Momentum = ?

Q94. Why are airbags used in cars?

Q95. A man jumps off a boat. Boat moves backward because:

Q96. A force of 10 N acts on 2 kg object for 3 s. Change in momentum = ?

Q97. Force required to stop 1000 kg car moving with 10 m/s in 5 s = ?

Q98. A bullet of mass 0.02 kg moving with 300 m/s hits wall, comes to rest in 0.01 s. Force = ?

Q99. A 2 kg object moving at 4 m/s has same momentum as:

Q100. Conservation of momentum is applicable when:

Login with your site account

Register a new account

Search

Modal title