Question

In a factory, it is desired to lift 2000 kg of metal through a distance of 12 m in 1 minute. Find the minimum horsepower of the engine to be used A .
Concept of Physics - 1 , HC VERMA , Chapter " Work and Energy"

Answer 1

Given in the Question :-
Mass of the metal m = 2000 kg.
height of the lift  h = 12 m.
Time t = 1 min = 60 sec.
So , here minimum work done by the system at the time metal lifted slowly. 

Now work done against the gravity ,
= mgh
= 2000 × 9.8 × 12
W= 235200 J.
Now for the Power, P = W/t
P= 235200 / 60
P = 3920 W.

Minimum horse power is req. 
P = 3920 /746     [ 1 hp = 746 W.]
P = 5.25 hp

Hence minimum power is req. is 5.25 hp.


Hope it Helps. :-)

Answer 2

HEY!!

_____________________________

✴Mass of the metal, m=2000 kg

✴Distance, s = 12 m

✴Time taken, t = 1 minute = 60 s

✴Force applied by the engine to lift the metal,

✴F = mg

✴So, work done by the engine, 

✴W= F×s× cos θ= mgs× cos 0° [θ= 0°  for  minimum  force]   

✴2000×10×12   

✴240000 J

✴So, power exerted by the engine,

✴P=W/t

✴240000^60= 4000 watt

▶▶Power in hp,

✔✔✔P= 4000/746=5.3 hp