Question

4.) A body is travelling due east at a speed of 15 km/h for one hour and then
turns towards south at a speed of 10 km/h for one hour. Find the average
velocity of the body.​

Answer 1

Answer:

Given that :

The body travelled towards the east at speed of 15 km/hr for 1 hr.

Then the body travelled towards the south at the speed of 10 km/hr for 1 hr.

We need to find the average velocity of the body.

We already know that the average velocity of a body is displacement per unit time.

Here, the total time taken by the body = 1 + 1 hr = 2 hr.

Now, let us find the displacement of the body.

The (red coloured) vector joining the tail of one vector to the other is the displacement vector for the body.

[Refer the attachement]

Applying Pythagoras theorem,

Displacement = √(15² + 10²)

⇒ √(225 + 100)

⇒ √325

⇒ 18.02

⇒ 18 km

So the average velocity = 18/2 = 9 km/hr