(a) The speed does not matter, since the kinetic energy does not change.
Multiply the weight M*g = 725 N by the vertical rise 90 sin30 = 45 m. You should get 32,630 Joules.
(b) Power = (Work done)/(Time required)
The time required is (90 m)/(3 m/s) = 30 s.
Power = 32,630/30 = 1088 Watts
= 1.45 hp
A skier of mass 74 kg is pulled up a slope by a motor-driven cable.
(a) How much work is required to pull him 90 m up a 30° slope (assumed frictionless) at a constant speed of 3.0 m/s?
J
(b) What power (expressed in hp) must a motor have to perform this task?
hp
2 answers
a) Work=Force x distance
To find force take your weight (74 kg) and multiply it by gravity (9.8) to get a force of 725 N
Next, find your distance by doing sin(30) times how many meters up the slope (90 m)
So then Work=(725)(45)= 32,625 J
To find force take your weight (74 kg) and multiply it by gravity (9.8) to get a force of 725 N
Next, find your distance by doing sin(30) times how many meters up the slope (90 m)
So then Work=(725)(45)= 32,625 J
1 answer