Question

A 20.0 kg block is being pushed forward on a flat surface with a force of magnitude 45.0 N against a frictional force of 13.0 N.

how would I find the change in kinetic energy after the force has pushed the block 4 meters?
how much work would it take to stop the block?
work done by 45 N force = 45 * 4 = 180 Joules
work lost to friction = 13 * 4 = 52 Joules
so gain in Ke = 180 - 52 = 128 Joules

then to stop you must remove that 128 Joules of Ke. If you just leave it alone the friction will stop it but in more than 4 meters

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