Question

The diagram below shows a pulley system, a mass of 10kg is raised 2m by an effort of 80N.

1. Calculate the distance moved by effort.
2. How much potential energy does the load gain?
3. How much work is done by the effort?
4. What is the efficiency of these pulleys?
5. Explain why it easier to tighten or loosen a nut using a spanner with a long handle than one with a short handle. 

Answer 1

1. Calculate the distance moved by effort. 
   • V.R = 2 = ^{(Distance moved by load)}/_{(Distance moved by effort)}
     2 = ^x/₂
     2x = 2m
     x = 1m
2. How much potential energy does the load gain? 
   • P.E = mgh
     = 10 x 10 x 2
     = 200J
3. How much work is done by the effort? 
   • Work input = Effort x Effort distance
     = 80N x 1m
     = 80 Joules
4. What is the efficiency of these pulleys? 
   • MA/VR x 100% = efficiency
     (¹⁰⁰/₈₀)/2 x 100% = ⁵⁰⁰⁰/₈₀
     Eff = 62.5%
5. Explain why it easier to tighten or loosen a nut using a spanner with a long handle than one with a short handle. 
   • With long handle spanner the effort used is less than short handle spanner so one does a lot of work