Question

1. find the efficiency of a machine that has an input work of 1200 j and an output work of 80 j (a) 0.56 % (b) 100 % (c) 6.67% (d) 80 % (e) none of the above

Explanation:

Step1: Recall efficiency formula

The formula for efficiency $\eta$ of a machine is $\eta=\frac{W_{out}}{W_{in}}\times100\%$, where $W_{out}$ is the output work and $W_{in}$ is the input work.

Step2: Substitute values

Given $W_{in} = 1200\ J$ and $W_{out}=80\ J$. Substitute into the formula: $\eta=\frac{80}{1200}\times 100\%$.

Step3: Calculate the result

$\frac{80}{1200}\times100\%=\frac{8000}{1200}\% \approx 6.67\%$

Answer:

C. $6.67\%$