Physics Questions and Answers – Laws of Motion Basics

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This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Laws of Motion Basics”.

1. Which of the following laws of motion is related to inertia?
a) First law
b) Second Law
c) Third Law
d) Fourth Law
View Answer

Answer: a
Explanation: The first law of motion states that a body remains in the state of motion or in the state of rest until and unless an external force is applied on it. This is also known as the law of inertia. Hence the answer is, the first law.
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2. Which law of Newton helps in finding the force on a body?
a) First law
b) Second Law
c) Third Law
d) Fourth Law
View Answer

Answer: b
Explanation: The second law of motion states that the net force applied on a body is proportional to the rate of change of momentum. On further experimentation, it was found that the force applied on a body is equal to the rate of change of momentum.

3. Which law of Newton helps in finding the reaction forces on a body?
a) First law
b) Second Law
c) Third Law
d) Fourth Law
View Answer

Answer: c
Explanation: The third law of motion states that for every action there is an equal and opposite reaction. This law helps us in finding the reaction forces on a body. A classic example is the way we walk. We need to push the ground for walking and when we do so we experience an equal and opposite force on ourselves which helps us in walking.
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4. The second law of motion, in mathematical form can be written as ____
a) F = dp/dt
b) F = ma
c) F = v(dm/dt)
d) F = mv
View Answer

Answer: a
Explanation: The second law of motion states that the net force applied on a body is equal to the rate of change of momentum. Momentum is usually represented by ‘p’. Hence, the answer is F = dp/dt.

5. When we walk on a boat in still water, the boat will ______
a) Move ahead
b) Move backwards
c) Not move
d) Move sideways
View Answer

Answer: b
Explanation: The third law of motion applies in this case. According to the third law of motion, for every action, there is an equal and opposite reaction. When we walk on the boat, the boat experiences an equal and opposite reaction force. Since very little resistance is offered by the still water, the boat will move backwards.
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6. Which one of the following is not an example of the third law of motion?
a) Walking
b) Skiing
c) Walking on a boat
d) Cycling
View Answer

Answer: b
Explanation: The third law of motion does not apply to skiing as in skiing we do not apply any force on the ground. The motion is caused by gravity and extremely less friction. In all the other cases, a force is applied on the ground or the other body, the reaction of which causes the motion.

7. Which of the following is the correct formulation for the second law of motion?
a) F = m(dv/dt)
b) F = ma
c) F = v(dm/dt) + ma
d) F = mv2
View Answer

Answer: c
Explanation: The second law of motion states that the net force applied on a body is equal to the rate of change of momentum. Hence, F = dp/dt. p = mv. Therefore, F = m(dv/dt) + v(dm/dt) = v(dm/dt) + ma.
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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter