Forces and Laws of Motion Test

Result

Forces and Laws of Motion Test - 10

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Question 1
1 / -0

Use the following information to answer the next question.

Gyanendra is sitting in a car that is moving at a constant speed. Gyanendra is stationary with respect to the car. The car stops suddenly.

As the car stops, Gyanendra experiences a force in the

A
downward direction

B
backward direction

C
forward direction

D
upward direction

Solution

The direction of external force that causes the change in the state of rest of Gyanendra has to be determined. Initially, Gyanendra is stationary with respect to the car. As the car stops suddenly, Gyanendra experiences a force in the forward direction. This force makes Gyanendra to lean forward.

The correct answer is C.

Why alternative A is wrong:

Gyanendra would fall down on experiencing a force in the downward direction.

Why alternative B is wrong:

Gyanendra would fall backward on experiencing a force in the backward direction.

Why alternative D is wrong:

Gyanendra would be thrown upward on experiencing a force in the upward direction.

Question 2

1 / -0

Use the following information to answer the next question.

Different amounts of force are applied on four balls of different masses. The respective acceleration of each ball on the application of force is listed in the given table.
Ball	Mass (kg)	Acceleration (m/s²)
I	0.5	18.0
II	1.0	9.5
III	1.5	6.0
IV	2.0	3.0

The maximum force is applied on ball

I

II

III

IV

Solution

The force on a ball is given as,

F = m × a

Where, m = Mass of the ball

a = Acceleration of the ball

The respective force applied on each ball is listed in the following table.

Ball	Mass (kg)	Acceleration (m/s²)	Force (N)
I	0.5	18.0	9.0
II	1.0	9.5	9.5
III	1.5	6.0	9.0
IV	2.0	3.0	6.0

Hence, the maximum force is applied on ball II.

The correct answer is B.

Question 3
1 / -0

Use the following information to answer the next question.

Tom is going to school on a bicycle. He observes that the speed of the bicycle slows down gradually as he enters a sandy path.

The bicycle slows down on entering the sandy path because

A
an external force acts on it

B
an internal force acts on it

C
external forces stop acting on it

D
internal forces stop acting on it

Solution

When the bicycle enters the sandy path, an opposite frictional force acts on its tires. This force acts in the direction opposite to the motion of the bicycle such that its speed gradually decreases. Frictional force is an external force on the bicycle. Internal forces do not affect the motion of a bicycle.

The correct answer is A.