Question

A car travels a distance A to B at a speed of 40km/h and returns to A at a speed of 30km/h
(1) What is average velocity?

Answer 1

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• According to given problem,

(i) A car travels a distance from A to B at the speed of 40 km/hr and returns to A at a speed of 30 km/hr.

(ii) Let D denotes the distance (in km) from A to B.

(iii) Let S & V denote the (average speed) & (average velocity) of the car.

• From (i), (ii) & (iii) we get,

S = (Total travel-distance)/(Total travel-time) …. (1a)

V = (Net displacement)/(Total travel-time) …. (1b)

• From (1a) we get,

S = (D + D)/(D/40 + D/30)

or S = 2*10/(7/12) = 240/7 = 34.29 (km/hr)

• From (1b) we get,

V = (D - D)/(D/40 + D/30) = 0

Answer 2

Answer:

According to given problem,

(i) A car travels a distance from A to B at the speed of 40 km/hr and returns to A at a speed of 30 km/hr.

(ii) Let D denotes the distance (in km) from A to B.

(iii) Let S & V denote the (average speed) & (average velocity) of the car.

From (i), (ii) & (iii) we get,

S = (Total travel-distance)/(Total travel-time) …. (1a)

V = (Net displacement)/(Total travel-time) …. (1b)

From (1a) we get,

S = (D + D)/(D/40 + D/30)

or S = 2*10/(7/12) = 240/7 = 34.29 (km/hr)

From (1b) we get,

V = (D - D)/(D/40 + D/30) = 0