Chapter 4, Problem 53R

To determine

To calculate: Input work.

Answer to Problem 53R

Input work is $\underset{\_}{700\text{ J}}$

Explanation of Solution

Given:

Efficiency = $20\%$

Output work = $140\text{ J}$

Formula used:

Efficiency is given by,

$e=\frac{W_{\text{out}}}{W_{\text{in}}}\times 100$

where $W_{\text{out}}$ is output work and $W_{\text{in}}$ is input work.

Calculation:

Input work is calculated as:

$\begin{array}{l}e=\frac{W_{\text{out}}}{W_{\text{in}}}\times 100\\ W_{\text{in}}=\frac{W_{\text{out}}}{e}\times 100\\ \text{ =}\frac{140\text{ J}}{20}\times 100\\ =700\text{ J}\end{array}$

Conclusion:

Input work is $\underset{\_}{700\text{ J}}$