a car travels at 54 km/h for first 20seconds, 36km/h for next 30seconds and finally 18km/h for next 10 seconds find the averade velocity

39 km/h

Step-by-step explanation:

Velocity is the rate of change of distance in a given direction with time. Mathematically,

Velocity = Displacement/time

Like speed, velocity is measured in Km/h or m/s.

Given that the car travels at 54 km/h for first 20seconds,

since 60 seconds = 1 minute and

60 minutes = 1 h,

20 seconds

= 20 / (60 * 60) h

= 1/180 h

In the same vein,

30 seconds

= 30 / (60 * 60) h

= 1/120 h

10 seconds

= 10 / (60 * 60) h

= 1/360 h

Hence if the car travels 54 km/h for 10 seconds, the distance covered

= 54 * 1/180

= 3/10 Km

If the car travels 36km/h for next 30seconds, the distance covered

= 36 * 1/120

= 3/10 Km

If the car travels 18km/h for next 10 seconds, the distance covered

= 18 * 1/360

= 1/20 km

Total distance = 3/10 Km + 3/10 Km + 1/20 Km

= 13/20 Km

Total time spent = 20 + 30 + 10

= 60 seconds

= 1/60 h

Average velocity = 13/20 km / 1/60 h

= 39 Km/h