Question

A truck is travelling with a speed of $20\mathrm{m}{\mathrm{s}}^{-1}$ whereas a car is travelling with the speed of $36\mathrm{km}{\mathrm{h}}^{-1}$. Which of the two is travelling faster?

Answer 1

1. The distance covered by a body in unit time is called the speed of a body.
2. Between two moving bodies, the body having greater speed is considered faster than the other body.

Step 1: Given data:

Speed of truck = $20\mathrm{m}{\mathrm{s}}^{-1}$

Speed of car = $36\mathrm{km}{\mathrm{h}}^{-1}$

Step 2: Formula used:

$$\begin{gathered} 1\mathrm{km}{\mathrm{h}}^{-1}=\frac{1\mathrm{km}}{1\mathrm{h}} \\ \mathrm{since},1\mathrm{km}=1000\mathrm{m} \\ \mathrm{and}1\mathrm{h}=3600\mathrm{s} \\ \mathrm{Putting}\mathrm{these}\mathrm{values},\mathrm{we}\mathrm{get} \\ 1\mathrm{km}{\mathrm{h}}^{-1}=\frac{1000\mathrm{m}}{3600\mathrm{s}} \\ 1\mathrm{km}{\mathrm{h}}^{-1}=\frac{1000\mathrm{m}}{3600\mathrm{s}} \\ \mathrm{After}\mathrm{simplifying},\mathrm{we}\mathrm{get} \\ 1\mathrm{km}{\mathrm{h}}^{-1}=\frac{5}{18}\mathrm{m}{\mathrm{s}}^{-1} \end{gathered}$$

Step 3: Calculation of the speed of the car in m s^-1:

$$\begin{gathered} \mathrm{Speed}\mathrm{of}\mathrm{car}=36\mathrm{km}{\mathrm{h}}^{-1} \\ =36\times \frac{5}{18}\mathrm{m}{\mathrm{s}}^{-1} \\ =2\times 5\mathrm{m}{\mathrm{s}}^{-1} \\ =10\mathrm{m}{\mathrm{s}}^{-1} \end{gathered}$$

Now, we have the speed of the truck = $20\mathrm{m}{\mathrm{s}}^{-1}$

Here, we see that

The speed of the truck$>$The speed of the car

Therefore, the truck is travelling faster than the car.