# What is the kinetic energy of an object with a mass of #5# # kg# that has been in freefall for #12# #s#?

##### 1 Answer

There are two possible approaches, one of which involves finding the velocity and the other the distance traveled. Both yield the answer

#### Explanation:

There are a couple of possible approaches, and I'll briefly outline both, just for fun. The first is probably the most popular.

*First approach*

Find the velocity of the object. We assume no air resistance and an initial velocity of

Now calculate the kinetic energy:

*Second approach*

Find the distance fallen:

Then note that the change in gravitational potential energy will have been converted into kinetic energy. The change in gravitational potential energy will be:

It's always very reassuring to do the same question two different ways and get the same answer: which is one good reason to learn more than one way to do it!