# High School Physics : Understanding Kinetic and Potential Energies

## Example Questions

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### Example Question #11 : Energy

Laurence throws a  rock off the edge of a  tall building at an angle of  from the horizontal with an initial speed of .

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What is the vertical kinetic energy right before the rock hits the ground?

Explanation:

The formula for kinetic energy is:

Since the velocity we're working with is going to be in the vertical direction, we need to find the final . The best place to start is by finding the initial vertical velocity. To do that, we need to break the given velocity into its vertical component by using the sine function and the angle.

We know that the rock is going to travel a net of , as that's the displacement between the rock's initial position (on the building) and the ground. Using the appropriate motion equation, we can find the final velocity using the initial velocity, displacement, and acceleration.

Use this final vertical velocity and the mass of the rock to calculate the final kinetic energy in the vertical direction.

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