Physics
posted by Anonymous on .
please can u check my answer
Here are the questions:
1. A 0.45 kg book is resting on a dessktop 0.64 m high. Calculate the book's potential energy relative to
a)the desktop? b)the floor.
2. A 0.636 kg basketball has a potential energy of 19J at the basket. How high is the ball from the floor?
3. A hockey puck has a potential energy of 2.3J when it is held by a referee at a height of 1.4 m above the rink surface. calculate the mass of puck?
My solutions:(used Eg=mgh to get all solutions)
1. a) 2.8J b) 0
2. h=31m
3. 0.6176 kg

I think you reversed the answers on 1.
2. mgh=19
h= 19/(.636*9.8) didn't you miss the decimal place?
3. mgh=PE
m= 2.3/(1.4*9.8) not your answer. 
when i divided 2.3/(1.4*9.8) i got 0.1676
and for quesiton 1 do u mean that a) will be 0J sinse it is rest on the desktop and b) will be 2.8 J 
yes, and yes.