Question

A car travels a certain distance with a speed of 50 km/h & returns with a speed of 40 km/h. Calculate
(i) the average speed for the whole
journey.
(ii) average velocity of car for the whole journey.

Answer 1

Given:

forward journey speed of car, u = 50 $\frac{km}{h}$

return journey speed of car, v = 40 $\frac{km}{h}$

To Find:

i. average speed for the whole  journey

ii. average velocity of car for the whole journey

i. average speed = $\frac{u + v}{2}$

                            =  $\frac{50 + 40}{2}$ $\frac{km}{h}$

                            = 45 $\frac{km}{h}$

ii. average velocity =$\frac{displacement}{time}$

                               = 0  as displacement is 0 [the car returns back to it's initial position]

Answer 2

Answer:

Explanation:

1)Average speed=total distance/total time

In the first case-speed=50km/hr

Time=distance/speed=x/50

In the second case-speed=40km/hr

Time=distance/speed=x/40

Total distance therefore is 2x

Total time =x/50+x/40=90x/200

Avg speed=2x/90x/200

2x*200/9x

= 4.44 km/hr

Average velocity=v+u/2

=40+50/2

90/2

=45km/hr

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