# A roller coaster has a mass of 275 kg. It sits at the top of a hill with height 85 m. If it drops from this hill, how fast is it going when it reaches the bottom?

Nov 9, 2016

$\textsf{41 \textcolor{w h i t e}{x} \text{m/s}}$

#### Explanation:

The potential energy of the roller coaster is converted into kinetic energy when it reaches the bottom.

So we can write:

$\textsf{\cancel{m} g h = \frac{1}{2} \cancel{m} {v}^{2}}$

$\therefore$$\textsf{v = \sqrt{2 g h}}$

$\textsf{v = \sqrt{2 \times 9.8 \times 85} = 41 \textcolor{w h i t e}{x} \text{m/s}}$

As you can see, the mass given is irrelevant to the question.