Question

A truck driver driving at the speed of 54 km h^–1 notices a road sign with a speed limit of 40 km h^–1 (Fig.) for trucks. He slows down to 36 km h^–1 in 36 s. What was the distance travelled by him during this time? Assume the acceleration to be constant while slowing down.

Answer 1

The average velocity formula is the simplest method of calculating the distance (s) because the acceleration is constant:

s = `((u + v)/2) xx t`

Convert speed into m/s

u = 54km/hr = 15 m/s

v = 36 km/hr = 10 m/s

t = 36 s

Substituting the values:

s = `((15 + 10)/2) xx 36`

s = `(25/2) xx 36`

s = 12.5 × 36

s = 450 m

Hence, the distance travelled by the truck during this time is 450 m.