FALL 2002 QUIZ 1

PHYSICS 100A

1. A car starts from rest to motion with a velocity of 60km/hr in 8 seconds to the north. (a) What is the car's acceleration in m/s²? (b) What is the displacement of the car covers after this time interval? (b) What is the average velocity in m/s at this time interval? 

SOLUTION.

(a) We find the acceleration from

             a = Dv/Dt = [(60km/hr)(1000m/km)/(3.6ks/hr) - 0]/(8s) = 2.1m/s² (to the north).

(b) We find the displacement from

           Dx = v₀t + 1/2at² = 0 + 1/2(2.08m/s²)(8s)² = 66.6m. (to the north).

(c) We find the average velocity from

            v_av = Dx/Dt = 66.6m/8s = 8.3m/s (to the north).

     Or we can find the average velocity from

            v_av = (v₁ + v₂)/2  = [0 + (60km/hr)(1000m/km)/(3.6ks)]/2 = 8.3m/s (to the north).