Question

What is the change in momentum of a car weighing 1500 kg when its speed increases from 36 km/h to 72 km/h uniformly?

Answer 1

Step 1:Given:

Mass of car, $m=1500\hspace{0.17em}\text{kg}$.

Final velocity, $v_f=72\hspace{0.17em}\frac{\text{km}}{\text{h}}$.

Initial velocity,$v_i=36\hspace{0.17em}\frac{\text{km}}{\text{h}}$.

Step 2: Write an expression of change in momentum as follows:

$P=m\left(v_f-v_i\right)$

Step 3:Substituting values

$1500\hspace{0.17em}\text{kg}$ for $m$, $72\hspace{0.17em}\frac{\text{km}}{\text{h}}$ for $v_f$ and $36\hspace{0.17em}\frac{\text{km}}{\text{h}}$ for $v_i$ in expression of momentum:

$$\begin{gathered} P=1500\hspace{0.17em}\text{kg}\left(72-36\right)\left|\text{km}\right|\text{×}\frac{{10}^3\text{m}}{\left|\text{km}\right|}\text{×}\frac{\left|\text{h}\right|}{\left|\text{h}\right|\text{×3600 s}} \\ =15000\frac{\text{kg.m}}{\text{s}} \end{gathered}$$

Hence, the change in momentum of the car is $15000\frac{\text{kg.m}}{\text{s}}$.