The average work done by a human heart while it beats once is $0.5\mathrm{J}$. Calculate the power used by heart if it beats $72$ times in a minute.

A bob of mass $m$ suspended by a light string of length $L$ is whirled into a vertical circle as shown in figure. What will be the trajectory of the particle if the string is cut at

(a) Point B?

A bob of mass $m$ suspended by a light string of length $L$ is whirled into a vertical circle as shown in figure. What will be the trajectory of the particle if the string is cut at

(b) Point C?

A bob of mass $m$ suspended by a light string of length $L$ is whirled into a vertical circle as shown in figure. What will be the trajectory of the particle if the string is cut at

(c) Point X?

A graph of potential energy $V\left(x\right)$ versus $x$ is shown in figure. A particle of energy $E_o$ is executing motion in it. Draw graph of velocity and kinetic energy versus $x$ for one complete cycle .

Consider a one-dimensional motion of a particle with total energy $E$. There are four regions $A, B, C$ and $D$ in which the relation between potential energy $V$, kinetic energy $\left(K\right)$ and total energy $E$ is as given below:
Region $A: V>E$

Region $B: V<E$

Region $C: K>E$  

Region $\mathrm{D}: \mathrm{V}>\mathrm{K}$

State with reason in each case whether a particle can be found in the given region or not.