Question

If you drop a steel metal ball off a building and it takes 3 seconds to hit

the ground, how tall is the building?

Answer 1

`40\:\mathrm{m}`

Step-by-step explanation:

We can use kinematics equation
`\Delta y={v_i}^2+(1)/(2)at^2` to solve this problem. Because the metal ball's initial velocity was 0,
`{v_i}^2=0`.

Therefore, our equation becomes:

`\Delta y=(1)/(2)at^2` (freefall equation).

`t` is given as 3 seconds and
`a` is acceleration due to gravity (
`9.81\:\mathrm{m/s}`).

Therefore, our answer is:

`\Delta y = (1)/(2)\cdot9.81\cdot3^2=44.145=\fbox{$40\:\mathrm{m}$}` (one significant figure).