High School

The hopper of a concrete hoist weighs 750 lb when half loaded. If this hopper is raised 165 ft in 6.00 s, find the power required in:

(a) ft-lb/s
(b) hp
(c) W

Answer :

The power required to raise the concrete hopper is 20,625 ft-lb/s, 37.5 hp, and 27,214 W.

To find the power required to raise a concrete hopper, we need to apply the concept of work and power in physics.

  • Weight of the hopper (F): 750 lb
  • Height raised (h): 165 ft
  • Time taken (t): 6.00 s

(a) Power in ft-lb/s

First, we calculate the work done (W):

W = F × h

W = 750 lb × 165 ft = 123,750 ft-lb

Next, we calculate the power (P):

P = W ÷ t

P = 123,750 ft-lb ÷ 6.00 s = 20,625 ft-lb/s

(b) Power in hp

We know that 1 hp = 550 ft-lb/s. So, converting the power to horsepower:

P (hp) = 20,625 ft-lb/s ÷ 550 ft-lb/s = 37.5 hp

(c) Power in W

We know that 1 hp = 745.7 W. So, converting the power from horsepower to watts:

P (W) = 37.5 hp × 745.7 W/hp = 27,214 W