Physics Multiple Choice Questions on “Newton’s First Law of Motion”.
1. What causes the motion of a body which is initially in the state of rest?
a) Force
b) Displacement
c) Speed
d) Velocity
Answer: a
Clarification: 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. Hence, the answer is force. This is also known as the law of inertia.
2. People sitting in a moving bus experience a jerk when the bus stops. This is due to _____
a) Inertia of motion
b) Inertia of rest
c) Inertia of turning
d) Inertia of acceleration
Answer: a
Clarification: When the bus stops, the people sitting in it experience a jerk. This is because, while the bus was moving, the people were moving with it. Hence, they were having an inertia of motion. When the bus stops, the inertia of the bus changes from that of motion to that of rest. But the inertia of the people still remains that of motion. Hence, they experience a jerk.
3. Passengers sitting in a stationary car experience a jerk when the car suddenly starts. This is due to _____
a) Inertia of motion
b) Inertia of rest
c) Inertia of turning
d) Inertia of acceleration
Answer: b
Clarification: When the car starts, the people sitting in it experience a jerk. This is because, while the car was stationary, the people were stationary with it. Hence, they were having an inertia of rest. When the car starts, the inertia of the car changes from that of rest to that of motion. But the inertia of the people still remains that of rest. Hence, they experience a jerk.
4. In the following figure, what will happen to the ball hanging from the roof of the car if the car suddenly moves towards left (direction shown by arrow)?
a) Ball moves towards right
b) Ball moves towards left
c) Ball does not move
d) Ball moves out of the paper
Answer: a
Clarification: Since the system was initially at rest, the inertia of the ball is that of rest. When the car suddenly moves the inertia of the car changes but not that of the ball. Hence the ball moves towards right.
5. A straight moving bus takes a sharp right turn. What will happen to the passengers sitting inside the bus?
a) They will tilt rightwards
b) They will tilt leftwards
c) They will stay the way they were
d) They will start jumping
Answer: b
Clarification: When the bus takes a sharp right turn, the inertia of the bus changes. But the inertia of the passengers is still towards the straight direction. Hence, they will relatively move towards the left.
6. Why do we not experience any leaning when a train takes a turn?
a) Because the train is powerful
b) Because of large turning radius
c) Because the train does not turn
d) Because the driver is smart
Answer: b
Clarification: The train’s turning radius is large as compared to the turning radii of normal vehicles. Hence, there is no sharp or sudden turning. Therefore, the passengers do not experience any leaning.
7. Inertia is _____
a) Property of mass to remain unchanged
b) Property of mass to change continuously
c) Property of mass to accelerate
d) Tendency of mass to accelerate
Answer: c
Clarification: Inertia is the property of mass to remain unchanged. Inertia is because of which a mass continues to remain in its original state in absence of any external force. Inertia of a body can be changed only by an external force.