science
posted by Dave .
1. How much potential energy does a 5kg block have if it is 2m above the ground?
2. What is the mass of an object that has 40J of potential energy and is 10m above the ground?
3. What is the weight of an 8kg object?
4. How much work does it take to lift an 8kg object 2m?
5. How high up must you lift a 12kg object to give it 72J of potential energy?
6. A 5kg ball is rolling along the floor with a velocity of 3m/s. What is its kinetic energy?
7. The ball from question 6 speeds up to 6m/s. What is its new kinetic energy?
8. Compare your answers to questions 6 and 7. What do you notice about the kinetic energy when an object doubles its velocity?

Use the formulas:
(Potential energy) =
M g H = (Mass)*(g)*(height)
Weight = M*g
Kinetic energy of a rolling solid ball = (7/10) M V^2
(This includes the energy associated with rotation)
Show your work if you need further assistance. 
1.Given :h=2m,m=5kg potential energy=mgh=5Ã—10Ã—2=100 J

2.Given :potential energy=40J,h=10m Potential Energy =mgh since,
m=gh/P.E.=10*10/40J =20/40J =0.5kg 
what does gravity = ?

reply plz.

gravity = 9.8 on earth

thanks sky reaper.
5*9.8*2=98 
ok