# What is the kinetic energy of an object with a mass of #9 kg# that has been in freefall for #1 s#?

##### 2 Answers

The kinetic energy is approximately 433 J.

#### Explanation:

The kinetic energy, in classical mechanics, it is

You have the mass, so you need to calculate the velocity.

Your body is in free fall, this means that it is subject to the gravity that accelerates with a constant strength.

The acceleration is the change of velocity during the time. So we can write:

Then

With the velocity we can calculate the energy

I found:

#### Explanation:

We can think of our system in which the object was placed at a certain height and then released. Now, when it was placed at the initial position it gained a certain Potential Energy

We know that:

Potential Energy:

where:

From kinematics we have:

with:

so:

considering the ground as

and finally: