mr. franklin uses a machine that has an efficiency of 80%. the machine applies a force of 800 n through a…

Explanation:

Step1: Calculate the useful work output

Useful work output $W_{out}=F_{out}d_{out}$, where $F_{out} = 800\ N$ and $d_{out}=20\ m$. So $W_{out}=800\times20 = 16000\ J$.

Step2: Calculate the work input

The efficiency formula is $\eta=\frac{W_{out}}{W_{in}}$. Given $\eta = 0.8$ and $W_{out}=16000\ J$. We can find $W_{in}=\frac{W_{out}}{\eta}=\frac{16000}{0.8}=20000\ J$.

Step3: Calculate the input - distance

The work - input formula is $W_{in}=F_{in}d_{in}$, where $F_{in} = 50\ N$ and $W_{in}=20000\ J$. Then $d_{in}=\frac{W_{in}}{F_{in}}=\frac{20000}{50}=400\ m$.

Answer:

D. 400 m