Question
A moving company wants to lift a piano to the second story of a house and has these three pulley set ups to choose from (the piano would replace the weight pictured). Which would be the best choice and why?
(1 point)
Responses
Choice C because the pulley changes the directions of the pull and reduces the amount of force needed, even though the rope is pulled longer.
Choice C because the pulley changes the directions of the pull and reduces the amount of force needed, even though the rope is pulled longer.
Choice B would be the best, because you are pulling upwards using half of the force, so it would be easier.
Choice B would be the best, because you are pulling upwards using half of the force, so it would be easier.
Either A or B because the force will be the same (half) and the amount of rope pulled is the same and the directions does not matter.
Either A or B because the force will be the same (half) and the amount of rope pulled is the same and the directions does not matter.
Choice A would be the best because the pull motion is downward he will only use 1/2 of the force, so that will be easier.
Choice A would be the best because the pull motion is downward he will only use 1/2 of the force, so that will be easier.
Question 2
A man is using a pulley to raise a weight. He is applying 45 joules of energy to pull on that rope and 44.325 joules of energy are being used to lift the weight. What is the efficiency of the pulley?
(1 point)
Responses
98.325 joules
98.325 joules
1.015%
1.015%
.675 Joules
.675 Joules
98.5%
Answers
GPT-4o mini
For the first question regarding the best choice of pulley to lift a piano, the best response would be **Choice B**. This is because Choice B means that you are pulling upwards using half of the force, which makes it easier to lift the weight.
For the second question about the efficiency of the pulley, efficiency can be calculated using the formula:
\[
\text{Efficiency} = \left(\frac{\text{Useful Output Energy}}{\text{Input Energy}}\right) \times 100\%
\]
In this case, the useful output energy is 44.325 joules, and the input energy is 45 joules. So, the efficiency calculation would be:
\[
\text{Efficiency} = \left(\frac{44.325 \text{ Joules}}{45 \text{ Joules}}\right) \times 100\% \approx 98.25\%
\]
Given the options available, the closest answer for the efficiency of the pulley is **98.5%**.
For the second question about the efficiency of the pulley, efficiency can be calculated using the formula:
\[
\text{Efficiency} = \left(\frac{\text{Useful Output Energy}}{\text{Input Energy}}\right) \times 100\%
\]
In this case, the useful output energy is 44.325 joules, and the input energy is 45 joules. So, the efficiency calculation would be:
\[
\text{Efficiency} = \left(\frac{44.325 \text{ Joules}}{45 \text{ Joules}}\right) \times 100\% \approx 98.25\%
\]
Given the options available, the closest answer for the efficiency of the pulley is **98.5%**.