Chapter 9, Problem 37A

Calculate the power expended when a 20-N force pushes a cart 3.5 m in a time of 0.5 s.

$\begin{array}{l}\text{Gravitational potential energy}=\text{weight}\times \text{height}\\ \text{PE}=mgh\end{array}$

To determine

Power expended.

Answer to Problem 37A

  $P=140\text{W}$

Explanation of Solution

Given:

Force, $F=20\text{N}$

Displacement, $d=3.5\text{m}$

Time, $t=0.5\text{s}$

Formula Used:

Power is given as,

  $P=\frac{W}{t}=\frac{Fd}{t}$

Where, $W$ is work done, $F$ is force applied, $d$ is displacement and $t$ is time interval.

Calculation:

On substituting the given values in above relation,

  $\begin{array}{l}P=\frac{20\times 3.5}{0.5}\\ \Rightarrow P=140\text{W}\end{array}$

Conclusion:

Therefore, the power expended is $P=140\text{W}$ .