# If a coin is dropped from a height of 80 m, how fast will it be travelling when it hits the ground? What assumptions, if any, do you need to make?

Sep 13, 2017

${v}_{f} =$-$40 \frac{m}{s} \hat{j}$

#### Explanation:

In case of free fall

${v}_{f} = \sqrt{2 \cdot g \cdot h}$

so ${v}_{f} = \sqrt{2 \cdot 10 \cdot 80}$
${v}_{f} = 40 \frac{m}{s}$.

we didn't assumed anything .

The derivation of the equation is from 3rd equation of motion.