# Newton’s Second Law of Motion: Concept of a System| Dynamics: Force and Newton’s Laws of Motion| College Physics| Openstax| Problem 1

#### A 63.0-kg sprinter starts a race with an acceleration of $4.20\:m/s^2$. What is the net external force on him?

Solution:

The net force has a formula

$F=ma$

Substituting the given values, we have

$F=\left(63.0\:kg\right)\left(4.20\:m/s^2\right)$

$F=265\:N$