Question

You use a pulley to lift your bike to the ceiling for winter storage. when you bought the pulley, the salesman claimed that the pulley has a mechanical advantage of 10. while lifting the bike, you notice that the pulley is squeaking because it has rusted over the summer. you determine that the pulley now has an actual mechanical advantage of 3. what is its efficiency?

Answer 1

AMA- actual machine advantage
IMA- ideal / theoretical machine advantage

Efficiency = AMA / IMA
                 =3 / 10
                 =0.3

Answer 2

3

(actually over the theoretical