- #1

blackout85

- 28

- 1

A woman lifts a barbell 2.0m in 5.0s, beginning and ending at rest. If she lifts the same distance in 10s, the work done by her is:

I said it would be four times as much because I used 1/2mv^2. I placed the v I calculated from v=d/t into the kinetic equation. (.4)^2 (.2)^2

.16 is four times as much as .04. Is this right.

A 2kg block is thrown upward from a point 20m above the Earth's surface. At what height above the Earth's surface will the gravitational potential energy of the earth-block systme have increased by 500J.

work:

mgh= 2(9.81)(20m)= 392.4 --> potential

500J= mgh

500J = (2kg)(9.81) (h)

h= 25m

If someone could point me in the right direction of how to do this problem I would appreciate it. Thank you.