Question

a car travels 30km at a uniform speed of 40km/hr and the next 30km at a uniform speed of 20km/hr. find its overage speed. with full explanation?​

Answer 1

Given :

▪ A car travels first 30km at a speed of 40kmph and last 30kmph at a speed of 20kmph.

To Find :

▪ Average speed of car during the whole journey.

Concept :

☞ Average speed is defined as the ratio of total distanve travelled to the total time taken.

☞ It is a scalar quantity.

☞ It has only magnitude.

☞ It can't be negative or zero.

☞ SI unit : m/s

Calculation :

→ Vav = (d1+d2)/(t1+t2)

→ Vav = (d1+d2)/[(d1/V1)+(d2/V2)]

→ Vav = (30+30)/[(30/40)+(30/20)]

→ Vav = 2×40×20/(40+20)

→ Vav = 1600/60

→ Vav = 26.67kmph

Answer 2

Given :

• S1 = 40 km/hr

• D1 = 30 km

• S2 = 20 km/hr

• D2 = 30 km

• Hence time T1 = D/S = 30/40 hr and

• T2 = D/S = 30/20

To Find :

• Average speed = ?

Figure :

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Solution :

Total Distance = D1 + D2 = 30 + 30 = 60 km

Total Time = T1 + T2 = 30/40 + 30/20 = 9/4 hr

Hence, Average speed = Total Distance / Total time

➩ Average speed = 60 / 9/4

➩ Average speed = 60 × 4/9

➩ Average speed = 26.67 km/hr

Therefore, average speed is 26.67 km/hr.