# College Physics 4.1 – The net external force on a sprinter

## Solution:

From Newton’s Second Law of Motion, the net external force on a body is equal to the product of its mass and acceleration. Therefore,

$\displaystyle \sum \text{F}=\text{ma}$

$\displaystyle \sum \text{F}=\left(63.0\:\text{kg}\right)\left(4.20\:\text{m/s}^2\right)$

$\displaystyle \sum \:\text{F}=264.6\:\text{kg}\cdot \text{m/s}^2$

$\displaystyle \sum \:\text{F}=264.6\:\text{N}$

The net external force on the sprinter is $264.6\:\text{newtons}$