Embibe Experts Solutions for Chapter: Work, Energy and Power, Exercise 2: Exercise-2

If a spring extends by $x$ on loading, then the energy stored by the spring is (if $T$ is tension in the spring and $k$ is spring constant)

A block of mass $2 \mathrm{kg}$ is free to move along the $x$-axis. It is at rest and from $t=0$ onwards it is subjected to a time-dependent force $F\left(t\right)$ in the $x$ direction. The force $F\left(t\right)$ varies with $t$ as shown in the figure. The kinetic energy of the block after $4.5$ seconds is:

When a work is done on a body by an external force then, its

If $W_1, W_2$ and $W_3$ represent the work done in moving a particle from $A$ to $B$ along three different paths $1 , 2, 3$ respectively (as shown) in the gravitational field of a point mass $m,$ find the correct relation between $W_1, W_2$ and $W_3$

Assertion : The instantaneous power of an agent is measured as the dot product of instantaneous velocity and the force (only one force applied by agent) acting on it at that instant.

Reason : The unit of instantaneous power is watt.

Assertion : Water at the foot of the water fall is always at different temperature from that at the top.

Reason : The potential energy of water at the top is converted into heat energy at the foot of the water fall.

Assertion : Graph between potential energy of a spring versus the extension or compression of the spring is a straight line.

Reason : Potential energy of a stretched or compressed spring is proportional to square of extension or compression.

Assertion : When the force retards the motion of a body, the work done is zero.

Reason : Work done depends on angle between force and displacement.