Question

Find the force necessary to stop a 900. kg jetta traveling at +25 m/s in a time of 5.0 seconds. (2sigfigs)(include units)

Answer 1

Given data:

* The mass of the object is m = 900 kg.

* The initial velocity of the object is u = 25 m/s.

* The final velocity of the object is v = 0 m/s.

* The time taken by the object is t = 5 seconds.

Solution:

The force required to stop the object is,

$F=\frac{m(v-u)}{t}$

Substituting the known values,

$\begin{gathered} F=\frac{900\times(0-25)}{5} \\ F=-\frac{900\times25}{5} \\ F=-4500\text{ N} \\ F=-4.5\times10^3\text{ N} \\ F=-4.5\text{ kN} \end{gathered}$

Here, the negative sign indicates the force is applied in the opposite direction to the direction of motion of an object.

Thus, the force applied to the object is - 4.5 kN.