physics
posted by TRACY on .
A 7 kilogram bowling ball is dropped from a fourth story window. If each story is 3 meters high, use energy conservation (not the equations of motion) to find the ball's velocity when it strikes the ground. Ignore air resistance.
1/2 m v^2= mgh
v= sqrt (2g*(3+.5))
V=sqrt(2)(9.8)(3)
v=sqrt58.8
v=7.67 m/s
did I do this right? thanks

Calculate potential energy first, the mass times gravity times the height. Four storeys and each one is 3 m, that's a height of 12 m.
12*9.81*7 = 824.04 J
Put that into the kinetic energy formula and rearrange to solve for velocity:
√((E*2)/(m))
or
√((824.04*2)/(7))
The velocity at landing is 15.34 m/s.