A 2.1 kg ball is attached to a ceiling by a string. The distance from the ceiling to the center of the ball is 0.81 m, and the height of the room is 3.00 m.
(a) What is the gravitational potential energy associated with the ball relative to the ceiling?
J
(b) What is the gravitational potential energy associated with the ball relative to the floor?
J
(c) What is the gravitational potential energy associated with the ball relative to a point at the same elevation as the ball?
J
2007-12-14 01:50:39 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
(a) No such luck. Pe= - mgh1 Notice a negative sign. Potential energy is the energy stored due to gravity (in this case) in the object relative to a particular point. Since the force of gravity is pointing down from the center of the ball and away from the ceiling the ball has a negative potential energy or it needs energy to reach the ceiling.
Pe= 2.1 x 9.81 x ( - .81)= -17 J
b) This is straight forward
Pe=mgh2 = 2.1 x 9.81 x (3.0 - .81)= 45J
c) Pe=0 J since h=0
2007-12-14 01:55:47 · answer #1 · answered by Edward 7 · 0⤊ 1⤋
Gravitational potential energy near the surface of the Earth is always mgh, where h is measured from wherever the origin of the coordinate system happens to be.
(a) mgh where h = -.81 m
(b) mgh where h = +2.29 m
(c) mgh where h = 0
2007-12-14 09:55:31 · answer #2 · answered by jgoulden 7 · 0⤊ 1⤋
a) P.E.=mgh=2.1*10*0.81
b) mgh=2.1*10*3
sry i can't fighure out c
2007-12-14 09:55:28 · answer #3 · answered by lp342 4 · 0⤊ 2⤋