Question

A car starts from rest and accelerates uniformly to 20 m s^–1 in 5 seconds. It then travels at 20 m s^–1 for 10 seconds and finally applies the brake (with uniform acceleration) to stop in 6 seconds. Find the total distance travelled.

Answer 1

Phase 1: Acceleration (0 to 20 m/s in 5 s)

Given: u = 0 ms^–1

v = 20 m/s

S₁ = `((0 + 20)/2) xx 5`

= 10 × 5

= 50m

Phase 2: Constant speed (20 m/s for 10 s)

S₂ = 20 × 10

= 200m

Phase 3: Deceleration (20 m/s to 0 in 6 s)

S₃ = `((20 + 0)/2) xx 6`

= 10 × 6

= 60m

∴ Total distance travelled = S₁ + S₂ + S₃

= 50 + 200 + 60

= 310 m

Hence, the total distance travelled by the car is 310 m.