Question

A car travels from stop A to stop B with a speed of 30 km/h and returns back to A with a speed of 50 km h. Find i)Displacement of the car. ii)Distance traveled by the car. iii) Average speed of the car.

Answer 1

Displacement of the car is zero as it is returned to its initial position.
1) Distance travelled by the car

We have to know how long it took for the round trip to find the distance:Lets assume it took 12 hrs for the round trip:let d = the one way distance

Write a time equation; time = dist/speed
d/30 + d/50 = 12

multiply by 150

150*d/30 + 150*d/50 = 150(12)

Cancel the denominators and you have:5d + 3d = 18008d = 1800d = 1800/8d = 225 m one way or a total of 450 m round trip

Confirm this find the actual time each way225/30 = 7.5 hrs

225/50 = 4.5 hrs

total hr: 12

2) average speed

v = 30 km/h

t = s/v

t = x/30 h

v= 50km/h

s=x

t= x/50 h

total distance= x+x =2x

total time= x/30 +x/50 = 5x +3x/150 = 8x/150

average speed = 2x / (8x/150)

= 2x * 150/8x = 37.5 km/h