A car starts from rest, then accelerates at 1.20 m/s² for 7.00 s. It hits the brakes, slowing to a stop at a rate of -4.25 m/s². What is the total distance travelled?

Answer 1

For the first part, use Δx₁ = v_o t + (1/2) a t² = 0 + (0.5)(1.20)(7.00)² = 29.4m.

For the second part, we will need the velocity v₁ attained before hitting the brakes: v₁ = v_o + a t = 0 + (1.20)(7.00) = 8.40 m/s. Then use v₂² = v₁² + 2a Δx₂, 0 = (8.4)² + 2(-4.25) Δx₂, 8.50 Δx₂ = 70.56, and Δx₂ = 8.3m. Total distance = Δx₁ + Δx₂ = 37.7m.