a body of mass m moving with velocity 3kmh collides with a

A body of mass $$m$$ moving with velocity $$3\,km/h$$ collides with a body of mass $$2 m$$ at rest. Now, the coalesced mass starts to move with a velocity

A. $$1\,km/h$$

B. $$2\,km/h$$

C. $$3\,km/h$$

D. $$4\,km/h$$

Answer : $$1\,km/h$$

Solution :
Work Energy and Power mcq solution image

Let $$v$$ be velocity of combined mass after collision.
Applying law of conservation of linear momentum
Initial momentum = Final momentum
$$\eqalign{ & m \times 3 + 2m \times 0 = \left( {m + 2m} \right)v \cr & {\text{or}}\,\,3m = 3mv\,\,{\text{or}}\,\,v = 1\,km/h \cr} $$

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Releted Question 1

If a machine is lubricated with oil-

A. the mechanical advantage of the machine increases.

B. the mechanical efficiency of the machine increases.

C. both its mechanical advantage and efficiency increase.

D. its efficiency increases, but its mechanical advantage decreases.

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Releted Question 2

Two masses of $$1 \,gm$$ and $$4 \,gm$$ are moving with equal kinetic energies. The ratio of the magnitudes of their linear momenta is-

A. $$4:1$$

B. $$\sqrt 2 :1$$

C. $$1:2$$

D. $$1:16$$

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Releted Question 3

A particle of mass $$m$$ is moving in a circular path of constant radius $$r$$ such that its centripetal acceleration $${a_c}$$ is varying with time $$t$$ as $${a_c} = {k^2}r{t^2}$$ where $$k$$ is a constant. The power delivered to the particles by the force acting on it is:

A. $$2\pi m{k^2}{r^2}t$$

B. $$m{k^2}{r^2}t$$

C. $$\frac{{\left( {m{k^4}{r^2}{t^5}} \right)}}{3}$$

D. Zero

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Releted Question 4

A spring of force-constant $$k$$ is cut into two pieces such that one piece is double the length of the other. Then the long piece will have a force-constant of-

A. $$\left( {\frac{2}{3}} \right)k$$

B. $$\left( {\frac{3}{2}} \right)k$$

C. $$3k$$

D. $$6k$$

View Answer

A body of mass $$m$$ moving with velocity $$3\,km/h$$ collides with a body of mass $$2 m$$ at rest. Now, the coalesced mass starts to move with a velocity

Releted MCQ Question on
Basic Physics >> Work Energy and Power

If a machine is lubricated with oil-

Two masses of $$1 \,gm$$ and $$4 \,gm$$ are moving with equal kinetic energies. The ratio of the magnitudes of their linear momenta is-

A particle of mass $$m$$ is moving in a circular path of constant radius $$r$$ such that its centripetal acceleration $${a_c}$$ is varying with time $$t$$ as $${a_c} = {k^2}r{t^2}$$ where $$k$$ is a constant. The power delivered to the particles by the force acting on it is:

A spring of force-constant $$k$$ is cut into two pieces such that one piece is double the length of the other. Then the long piece will have a force-constant of-

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Work Energy and Power

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A body of mass $$m$$ moving with velocity $$3\,km/h$$ collides with a body of mass $$2 m$$ at rest. Now, the coalesced mass starts to move with a velocity

Releted MCQ Question on Basic Physics >> Work Energy and Power

If a machine is lubricated with oil-

Two masses of $$1 \,gm$$ and $$4 \,gm$$ are moving with equal kinetic energies. The ratio of the magnitudes of their linear momenta is-

A particle of mass $$m$$ is moving in a circular path of constant radius $$r$$ such that its centripetal acceleration $${a_c}$$ is varying with time $$t$$ as $${a_c} = {k^2}r{t^2}$$ where $$k$$ is a constant. The power delivered to the particles by the force acting on it is:

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