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Linear momentum of a system is conserved only if the net external force acting on the system is zero.

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Important Questions on Laws of Motion

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A ball of mass $10 kg$ moving with a velocity $10 \sqrt{3} m s^{- 1}$ along the $x$ -axis, hits another ball of mass $20 kg$ which is at rest. After the collision, first ball comes to rest while the second ball disintegrates into two equal pieces. One piece starts moving along $y$ -axis with a speed of $10 m s^{- 1} .$ The second piece starts moving at an angle of $30 °$ with respect to the $x$ -axis. The velocity of the ball moving at $30 °$ with $x$ -axis is $x m s^{- 1} .$ The configuration of pieces after the collision is shown in the figure below. The value of $x$ to the nearest integer is

Question Image

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

Two particles which are initially at rest move towards each other under the action of their mutual attraction. If their speeds are

v

and

2 v

at any instant, then the speed of center of mass of the system is,

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

An object of mass

m_{1}

collides with another object of mass

m_{2}

, which is at rest. After the collision the objects move with equal speeds in opposite direction. The ratio of the masses

m_{2} : m_{1}

is :

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A man of

60 kg

is running on the road and suddenly jumps into a stationary trolly car of mass

120 kg

. Then the trolly car starts moving with velocity

2 {m s}^{- 1}

. The velocity of the running man was _____

m s^{- 1}

, when he jumps into the car.

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A mass

M

attached to a horizontal spring executes

S . H . M .

of amplitude

A_{1}

. When the mass

M

passes through its mean position, then a smaller mass

m

is placed over it and both of them move together with amplitude

A_{2}

. The ratio of

(\frac{A_{1}}{A_{2}})

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A bullet of mass

50 g

is fired from a rifle of mass

2 kg

and the total kinetic energy produced by the explosion is

2050 J

. Then the kinetic energy of the bullet and the rifle are

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A stationary body explodes into two parts of masses

M_{1}

and

M_{2}

. They move in opposite directions with velocities

v_{1}

and

v_{2}

. The ratio of their kinetic energies is

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

An object

A

of mass

20 kg

and travelling at

20 m s^{- 1}

crashes into another object

B

of mass

200 kg

and travelling at

10 m s^{- 1},

in the same direction. After the collision, object

A

bounces back in opposite direction at a speed of

10 m s^{- 1}

. The speed of the object

B

after the collision is

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A body of weight

W_{1}

is suspended from the ceiling of a room through a chain of weight

W_{2} .

The ceiling pulls the chain by a force

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A body of mass

(4 m)

is lying in

x

y

plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass

(m)

move perpendicular to each other with equal speeds

(υ) .

The total kinetic energy generated due to explosion is:

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A bomb at rest explodes into

3

parts of same mass. The momentum of two parts is

- 3 p \hat{i}

and

2 p \hat{j}

respectively. The magnitude of momentum of the third part is

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A balloon with mass

m

is descending down with an acceleration

a

(where

a < g) .

How much mass should be removed from it so that it starts moving up with an acceleration

a

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A particle having a mass

0.5 kg

is projected under gravity with a speed of

98 m \sec^{- 1}

at an angle of

60 °

. The magnitude of the change in momentum (in

N \sec

) of the particle after

10 seconds

[g = 9.8 m s^{- 2}]

HARD

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A man (mass

= 50 k g

) and his son (mass

= 20 k g

) are standing on a frictionless surface facing each other. The man pushes his son so that he starts moving at a speed of

0.70 m s^{- 1}

with respect to the man. The speed of the man with respect to the surface is:

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A body of mass

M

moving with velocity

v

explodes into two equal parts. If one part comes to rest and the other part moves with velocity

v_{0}

; what would be the value of

v_{0}

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

Two blocks

A

and

B

of masses

3 m

and

m

respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of

A

and

B

immediately after the string is cut, are respectively
Question Image

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

Two blocks A and B masses

2 m

and

m,

respectively, are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in the figure. The magnitudes of acceleration of A and B, immediately after the string is cut, are respectively.
Question Image

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A string of negligible mass going over a clamped pulley of mass supports a block of mass M as shown in the figure. The force on the pulley by the clamp is given by

Question Image

EASY

Physics>Mechanics>Laws of Motion>Conservation of Momentum

A thread from the ceiling of a car suspends a ball. The brakes are applied and the car decelerates at

2 m s^{- 2}

. If the ball comes to equilibrium at an angle

θ

from the vertical, then

θ

must be

(g = 10 m s^{- 2})

MEDIUM

Physics>Mechanics>Laws of Motion>Conservation of Momentum

Consider a system of two solid balls connect by a light spring in air which is horizontal at the given instant. The horizontal acceleration of the 10 kg ball is

12 m / s^{2}

towards right at the given instant. What would be the total acceleration of the 20 kg ball, if it starts falling? (take

g = 10 m / s^{2}

)

Linear momentum of a system is conserved only if the net external force acting on the system is zero.

Important Questions on Laws of Motion

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