Question

A car travels from stop A to stop B with a speed of 30 km/h and then returns back to A

with a speed of 50 km/h. Find

(i) displacement of the car.

(ii) distance traveled by the car.

(iii) average speed of the car.​

Answer 1

Given :

A car travels from stop A to stop B with a speed of 30 km/h and then returns back to A with a speed of 50 km/h.

To find :

(i) displacement of the car.

(ii) distance travelled by the car.

(iii) average speed of the car.

Solution :

Answer (i) :-

The displacement of the car is zero. Because displacement is the shortest path travelled by an object or the path travelled by an object in a particular distance. And if the body travels a particular distance and then comes back to its starting point the displacement becomes zero but the body has covered some distance.

Therefore,

• Displacement of the car is zero

Answer (ii) :-

Let the distance travelled by the car from point A to B be x km.

So, when it travels back to point B. It's distance will be :-

→ x + x

→ 2x km

Therefore,

• Distance travelled by the car = 2x km

Answer (iii) :-

Now, we will calculate the average speed :-

For that firstly, we shall calculate the time.

Formula to calculate time :-

• Time = Distance ÷ Speed

Time taken to travel from stop A to B :-

→ Time = x/30 hr

Time taken to travel from stop B to A :-

→ Time = x/50 hr

→ Total time = x/30 + x/50

→ Total time = (5x + 3x)/150

→ Total time = 8x/150

Now, using formula :-

Average speed = Total distance travelled ÷ Total time taken

we have,

Total distance travelled = 2x

Total time taken = 8x/150

Substituting the given values :-

→ Average speed = 2x ÷ 8x/150

→ Average speed = (2x × 150)/8x

→ Average speed = 150/4

→ Average speed = 37.5

Therefore, the average speed of the car = 37.5 km/h