Question

Car drag racing takes place over a distance of a 1 4 mile (402 m) from a standing start. If a car (mass 1500 kg) would be propelled forward with a pulling force equal to that of gravity, what would be the change in kinetic energy and the terminal speed of the car (in mph) at the end of the race be?

Answer 1

Answer:

The change in kinetic energy is 5,909,400J and the terminal speed of the car is 160,800mph

Explanation:

Change in kinetic energy = mg(h2 - h1)

Mass (m) = 1500kg, g = 9.8m/s^2, final distance (h2) = 402m, initial distance (h1) = 0m

Change in kinetic energy = 1500×9.8×(402 - 0) = 1500×9.8×402 = 5,909,400J

From equations of motion

h = ut + 1/2gt^2 [u is initial speed and is equal to zero because the car drag racing began from a standing start (rest)]

h = 1/2gt^2

402 = 1/2 × 9.8t^2

402 = 4.9t^2

t^2 = 402/4.9 = 82.04

t = √82.04 = 9.06s × 1h/3600s = 0.0025h

Terminal speed = distance/time = 402m/0.0025h = 160,800mph