Question 8 - Car Covering Different Distances Each Hour - Questions at the end of the chapter - Chapter 8 Class 7 - Measurement of Time and Motion (Curiosity)

Question. A car covers 60 km in the first hour, 70 km in the second hour, and 50 km in the third hour. Is the motion uniform? Justify your answer. Find the average speed of the car.

Answer.

Is the motion uniform?

• The car covers 60 km, 70 km, and 50 km in three equal time intervals.
• Distances are unequal in equal time intervals.
• So the motion is non-uniform .

Average Speed

Use the formula: Average speed = Total distance ÷ Total time

$$\begin{aligned} \text{Total distance} &= 60 + 70 + 50 \\[8pt] &= 180 \text{ km} \end{aligned}$$

$$\begin{aligned} \text{Total time} &= 1 + 1 + 1 \\[8pt] &= 3 \text{ h} \end{aligned}$$

$$\begin{aligned} \text{Average speed} &= \frac{\text{Total distance}}{\text{Total time}} \\[8pt] &= \frac{180 \text{ km}}{3 \text{ h}} \\[8pt] &= 60 \text{ km/h} \end{aligned}$$

The average speed is 60 km/h .