Question

A man spends $6.4KJ$ energy in displacing a body by $64m$ in the direction in which he applies force, in $2.5s$ Calculate:
(i) the force applied and
(ii) the power Spent (in HP) by the man

Answer 1

$\text{Step 1: Force applied}$

$\left(i\right)$ Work done by the man $=$ Force $\times$ distance moved in direction of force applied.
$W=F\times S$
$\Rightarrow 6.4\times {10}^{3}J=F\times 64m$

$\Rightarrow F=\frac{6.4\times {10}^3}{64}=100N$

$\text{Step 2: Power spent}$
$\left(ii\right)$ Power spent $=\frac{\text{Work done}}{\text{Time}}=\frac{6.4\times {10}^{3}J}{2.5s}=2560W$

$[\because 1H.P=746W\Rightarrow 1W=\frac{1}{746}H.P.]$
$\therefore$ Power spent in HP = $2560W=\frac{2560}{746}H.P=3.43H.P$