Forces and Laws of Motion Test

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Forces and Laws of Motion Test - 36

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Weekly Quiz Competition

Question 1
1 / -0

Choose the correct option.

A
Balanced forces do not have any impact on a body

B
Balanced force can change shape of an object

C
Unbalanced force do not produce motion

D
None

Solution

Balanced forces always produce motion.
Even though unbalanced forces do not produce motion, they can change the shape. E.g. when you press balloon from two sides in opposite directions.It does not move but it changes it's shape.
Question 2
1 / -0

If given is the direction of acceleration, where should the direction of force be?

A

B

C

D
None of these

Solution

Acceleration is produced in the same direction as Force. Hence, if the acceleration is towards the right, the force should also be applied in the right direction.
Question 3
1 / -0

A bowling ball hits a pin as shown, where $$F_{BP}$$ represents the force applied by the ball on the pin. Which arrow shows $$F_{PB}$$ (force applied by the pin on the ball) correctly?

A

B

C

D

Solution

From the third law of motion, $$F_{PB}$$ (reaction) is always equal and acts in the opposite direction to $$F_{BP}$$ (action).
Question 4
1 / -0

Which one of these is a real life application of the third law of motion?

A
Working of pulleys

B
Use of airbags in cars for safety

C
Helicopters creating lift by pushing air down

D
Cricketers pulling their hands down while taking a catch

Solution

The blades of a helicopter push the air down. Due to this action, it experiences an upward reaction force. Hence, it creates lift and flies.
Question 5
1 / -0

The acceleration of a body depends on:

A
The external force acting on the body only

B
The mass of the body only

C
Both the external force and the mass

D
The displacement of the body only

Solution

$$\text{Acceleration}=\dfrac{\text{External net force}}{\text{mass of the body}}$$
So, the acceleration depends on both the external force and the mass.

Note: If the motion is uniform acceleration(general case) then the displacement depends on acceleration not vice-versa.
Option C is correct.
Question 6
1 / -0

A nail driven into a wall by striking it with hammer is an example for

A
Force

B
Impulse

C
acceleration

D
mass

Solution

A nail driven into a wall by striking it with hammer is an example of Force. The more the force is applied by hammer, the more quickly the nail go inside the wall.
Question 7
1 / -0

Swimming is possible on account of :-

A
First law of motion

B
Second law of motion

C
Third law of motion

D
Newton's law of motion

Solution

Swimming is account on the newton's third law of motion since as we push the water we feel equal force by water on us and we move front
Question 8
1 / -0

The action and reaction force referred to in the third law

A
must act on the same object

B
must act on different object

C
may act on different object

D
act in the same direction

Solution

Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of force acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object.
Hence,
option $$B$$ is correct answer.
Question 9
1 / -0

An object of mass 10 kg moves at a constant speed of 10m/s. A constant force that acts for 4 sec on the object gives it a speed of 2m/s in opposite direction. The force acting on the object is:

A
-3N

B
-30N

C
3N

D
30N

Solution

Force is equal to the rate change of momentum. i.e $$\vec{F}=m \dfrac{d \vec{v}}{dt}$$
So, $$F= 10\times \dfrac{(-2)-10}{4} N = -30N$$
Question 10
1 / -0

A man is standing on a spring platform. The reading of spring balance is 60 kg wt. If the man jumps outside the platform, then the reading of the spring balance:

A
remains the same

B
decreases

C
increases

D
first increases and then decreases to zero

Solution

To jump off, the man exerts extra force on the springboard and hence the reading increases. But when the man leaves, the reading automatically decreases.