Question

The braking force needed to bring a 5000 kg truck to a stop from a speed of 25 m/s in 8 s is

Answer 1

Given:

The mass of the truck, m=5000 kg

The initial speed of the truck, u=25 m/s

The final speed of the truck, v=0 m/s

The time it takes for the truck to come to a stop, t=8 s

To find:

The braking force needed to bring the truck to a stop.

Explanation:

The acceleration of an object is the time rate of change of the velocity of the object.

Thus the acceleration of the truck is given by,

$a=\frac{v-u}{t}$

From Newton's second law of motion, the force needed to bring the truck to a stop is given by,

$\begin{gathered} F=ma \\ =m\times\frac{v-u}{t} \end{gathered}$

On substituting the known values,

$\begin{gathered} F=5000\times\frac{0-25}{8} \\ =-15625\text{ N} \end{gathered}$

The negative sign indicates that the force is applied in the direction opposite to the direction of motion of the truck.

Final answer:

Thus the braking force needed to bring the truck to a stop is 15625 N