Biophysics Problem 12

A high jumper jumps $1.2\; m$  straight up. With what speed did he leave the ground?

First Step

This is a straightforward problem in kinematics.

You should be able to make a list of three known variables and one unknown.

Make this list. Be careful with the sign of each quantity.

Variables

You should have the following:

known variables:
$s = 1.2\; m \\ v = 0 \\ a = -9.8\; m/s^2$

unknown variables:
$u = ?$

Now use the proper equation to solve for $u.$

The equation that you should use is:

$v^2 = u^2 + 2\;a\;s$

Calculations

$v^2 = u^2 + 2\;a\;s\\ u = \sqrt{v^2 - 2\;a\;s}\\ = \sqrt{0^2 - 2(-9.8)(1.2)}\\ = 4.9\frac{m}{s}$