Question

A mover hoists a 200 kg piano from the ground to a height of 10 m using a single pulley. What was the change in the pianos energy? a. 20j b. 200j c. 2000j d. 20000

Answer 1

P.E= Mass x gravity x height   (standard gravity = 10m/s approaximately)
     = 200x10x10= 20000j (D)

Answer 2

Answer: d. 20000 J

Explanation:

Potential energy is the energy possessed by an object by virtue of its position.

$P.E=m\times g\times h$

m= mass of object = 200 kg

g = acceleration due to gravity = $10ms^{-2}$

h = height of an object

1. when h= 10 m

$P.E=200\times 10ms^{-2}\times 10m=20000Joules$

2. when h= 0 m

$P.E=200\times 10ms^{-2}\times 0m=0Joules$

Thus change in energy=(20000-0)Joules=20000Joules.