A pulley system with 75% efficiency is set up to lift a 21kg bag of nails. The bag is lifted to a height of 2.3m by a person pulling on the rope with a force of 91.5N. What is the distance the rope must be pulled in order to lift the bag of nails?

Question

1711 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-11-18T22:46:22

#6.9"m"#

Work done on the load = Work done by the effort.

Since work done = force x distance moved in direction of force we can write:

#F_lxxD_l=F_exxD_e#

#:.( F_lD_l)/(F_eD_e)=1#

This is when the system is 100% efficient. Since it is 75% efficient we can write:

#(F_lD_l)/(F_eD_e)=0.75#

The load #F_l=21xx9.8=205.8"N"#

We need to find #D_e# so we can write:

#D_e= (F_lD_l)/(F_exx0.75)#

#:.D_e=(205.8xx2.3)/(91.5xx0.75)#

#D_e=6.9"m"#