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# Gravitational Potential Energy

### Gravitational Potential Energy

Gravitational Potential Energy governs how much energy is released by an object that is about to fall, and can be calculated using an equation.

Why is it that when you throw a ball up in the air it will always come back down?

What do you think we call the force which brings things down to Earth?

If you throw a $7 kg$ bowling ball up in the air, the Earth will pull it back with approximately $10$ Newtons per kilogram $(g=10N/kg)$. That's $70 N$ in total. So technically, $70N$ is the **weight** of the bowling ball.

Now, **Gravitational Potential Energy (GPE)** has to do with how much energy that could be released if an object started to fall. Take this example: A 60 kg hillwalker at an elevation of 1000 m has $GPE = 60kg \times 10 N/kg \times 1000m = 600,000 J$.

Have a go at calculating the GPE of a 150 kg llama grazing at a height of 3000 m.

Which equation do you think is the one we use for calculating gravitational potential energy (GPE)?

What do you think has more GPE; a 4kg cat on a 1m wall or a 0.4kg squirrel at the top of a 10m a tree?

What does the GPE equation **actually** tell us?

Imagine a body with GPE that begins to fall from its height. Have a guess as to what type of energy the GPE is mainly converted into.