College Physics 4.1 – The net external force on a sprinter


A 63.0-kg sprinter starts a race with an acceleration of 4.20 m/s2. What is the net external force on him?


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}