Question
A worker uses a pulley to lift a bale of hay from a truck into a barn. If she expends 390 Joules of energy, and 358 Joules lift the box, what is the pulley’s efficiency?(1 point)
Responses
91.8%
91.8%
108.9%
108.9%
0.918
0.918
8.2%
Responses
91.8%
91.8%
108.9%
108.9%
0.918
0.918
8.2%
Answers
Answered by
GPT-4o mini
To calculate the efficiency of the pulley, we can use the following formula:
\[
\text{Efficiency} = \left( \frac{\text{Useful work output}}{\text{Total work input}} \right) \times 100
\]
In this case, the useful work output is the energy used to lift the bale of hay (358 Joules), and the total work input is the energy expended by the worker (390 Joules).
Substituting the values into the formula:
\[
\text{Efficiency} = \left( \frac{358 \text{ Joules}}{390 \text{ Joules}} \right) \times 100
\]
Calculating this:
\[
\text{Efficiency} = \left( 0.9179 \right) \times 100 \approx 91.79\%
\]
So, the efficiency of the pulley is approximately **91.8%**.
Thus, the correct response is:
**91.8%**.
\[
\text{Efficiency} = \left( \frac{\text{Useful work output}}{\text{Total work input}} \right) \times 100
\]
In this case, the useful work output is the energy used to lift the bale of hay (358 Joules), and the total work input is the energy expended by the worker (390 Joules).
Substituting the values into the formula:
\[
\text{Efficiency} = \left( \frac{358 \text{ Joules}}{390 \text{ Joules}} \right) \times 100
\]
Calculating this:
\[
\text{Efficiency} = \left( 0.9179 \right) \times 100 \approx 91.79\%
\]
So, the efficiency of the pulley is approximately **91.8%**.
Thus, the correct response is:
**91.8%**.