Question

Les-6 A body travels half the distance with speed of 20m/s and other half with speed of 30m/
ne average speed of the body during whole journey is:
(a) Zero (b) 24m/s (c) 23m/s (d) none of these​

Answer 1

Answer :-

Given :-

• Speed in 1st half = 20 m/s
• Speed in 2nd half = 30 m/s

To Find :-

• Average speed during whole journey

Solution :-

If the distance travelled by object is same then,

$\implies\sf Average\: speed = \dfrac{2v_1v_2}{v_1+v_2}$

Here, as the body travels half distance in each time, the distance travelled by object is same in both case. So, we can find average speed by substituting the values in formula :-

$\implies\sf V_{avg} = \dfrac{2 \times 20 \times 30}{20 + 30}$

$\implies\sf V_{avg} = \dfrac{1200}{50}$

$\implies\sf V_{avg} = 12 \times 2$

$\implies\sf V_{avg} = 24$

Average speed during whole journey = 24 m/s

Answer 2

A N S W E R :

• Option (b) is correct

• Average speed during whole journey 24m/s

Given :

• A body covers half the distance with a speed of 2m/s and the other half with a speed of 30m/s

To find :

• Find Average speed during whole journey ?

Concept Used :

• Average speed is defined as ratio of total distance travelled to the total time take

Formula Used :

• If body covers first half of total distance with speed V1 and final half of total distance with speed V2, then average speed is given by,

v_av = 2v_1v_2/v_1 + v_2

Solution :

=> v_av = 2 × 20 × 30/20 + 30

=> v_av = 1200/50

=> v_av = 24m/s

Hence,

• Average speed during whole journey 24m/s

More Information :

• Average speed is scaler quantity
• Average velocity is vector quantity