Posted by **EJ** on Saturday, May 14, 2011 at 7:42pm.

A 10 kilogram object subjected to a 20 Newton force moves across a horizontal frictionless surface in the direction of the force. Before the force was applied, the speed of the object was 2.0 meters/second. When the force is removed the object is traveling at 6.0 meters per second. The initial kinetic energy is 20 J?

- Applied Physics -
**Damon**, Saturday, May 14, 2011 at 8:44pm
the kinetic energy = (1/2) m v^2

initially the speed is 2

so the initial Ke = (1/2)(10)(4) = 20 Joules

- Applied Physics -
**Damon**, Saturday, May 14, 2011 at 8:51pm
Now I suspect you will be asked what the final Ke is

(1/2)(10)(36) = 180 Joules

the increase in Ke = 180 - 20 = 160 Joules = work done by force

= Force*distance

so distance = 160/20 = 8 meters

now for time

Force * time = change in momentum

20 t = 10(6-2)

t = 40/20 = 2 seconds

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