Question

An extremely aerodynamic penny is thrown vertically downward off an observation tower. 4 seconds later, it impacts the ground 45m below. Find the impact velocity if g= 9.81m/s^2.

Answer 1

We have:

$$h=v_0t+0.5gt^2$$

$$45=v_0(4)+0.5(9.81)(4)^2$$

$$v_0=-8.37\frac{m}{s}$$

The direction was upwards.

$$v=v_0+gt=-8.37+9.81(4)=30.9\frac{m}{s}$$