Question

11. A DC-8 airplane reaches its takeoff speed of 78 s in a time of 35 s after starting from rest. What is its average acceleration? 14. The tires of a car begin to lose their grip on the ad at an acceleration of 5 m/s2. At this acceler- ation, how long does the car need to reach a speed of 25 m/s starting from 10 m/s?

Answer 1

Given speed (v) = 78 m/s time (t) = 35 sec The Average Acceleration (a_avg) = 78/35 = 2.228 m/s^2 (a_avg) = 2.28 m/s^2 Acceleration (a) = 5 m/s^2 Initial Velocity (V_a) = 10 m/s Final Velocity = (V_f) = 25 m/s acceleration (a) = (V_f - V_a/Time) Time = 25 - 10/acceleration = 15 m/s/5 m/s^2 Time = 3 sec