Question

A motor and gearbox system is used to raise a load from the ground to the roof of a building site. The load weighs 100kg and the motor runs from a 110 volt supply and draws a current of 15 amps. If the roof is 25m above the ground, calculate:

(a) The potential energy of the load when it has been raised
(b) Theamountofelectricalenergyusedinthattime
(c) The time taken to raise the load
(d) Theaveragespeedatwhichtheloadisbeingraised
(e) Thekineticenergyoftheloadwhenitisbeingraised.

Answer 1

Step-by-step explanation:

Given:

m = 100 kg

U = 110 W

I = 15 A

H = 25 m

g = 10 m/s²

__________

Wp - ?

A - ?

t - ?

V - ?

Wk - ?

(a) Potential energy of the load when it is lifted

Wp = m·g·H = 100·10·25 = 25 000 J

(b) The amountofelectri calenergyusedinth at time

E = I·U = 15·110 = 1550 J·s

c) The time taken to raise the load:

t = Wp / E = 25 000 / 1550 = 16 s

(d) The average speed at which the load is being raised

V = H / t = 25 / 16 ≈ 1.6 m/s

(e) The kinetic energy of the load when it is being raised.

Wk = m·V²/2 = 100·1.6² / 2 = 128 J