Question

A $2.0\times {10}^7$ kg train applies its brakes with the intent of slowing down at a $1.2m/s^2$ rate. What magnitude force must its brakes provide?

Short answer

Magnitude of force (F) provided by brakes =$2.4\times {10}^{7}N$.

Step-by-step solution

Force : 

The force exerted on a mass that causes it to change velocity.

Explanation : 

The quantity of force exerted on an object is equal to the product of its mass and the acceleration generated, according to Newton's second equation of motion.

$F=ma$

The object in this circumstance is a train that is slowing down by applying a brake.

Train mass $\left(m\right)=2.0\times {10}^{7}kg$,

Acceleration's magnitude $\left(a\right)=1.2m/s^2$,

$$\begin{gathered} F=ma \\ F=2\times {10}^7\times 1.2 \\ F=2.4\times {10}^{7}N \end{gathered}$$

Hence, by providing a force of magnitude $2.4\times {10}^{7}N$, brakes reduce train speed.