You are driving straight, travelling at 25 mph. You stomp on the brakes and come to a complete stop in a distance of 15 m. Assuming the brakes apply the same continuous force, if you are driving 50 mph when you apply the brakes, how far will your car travel before it comes to a stop?

60 m

Explanation:

Case 1:

v₀ = initial speed = 25 mph = 11.2 m/s

v = final speed = 0 m/s

a = acceleration = ?

d = stopping distance = 15 m

using the kinematics equation

v² = v₀² + 2 a d

0² = 11.2² + 2 a (15)

a = - 4.2 m/s²

Case 2:

v₀ = initial speed = 50 mph = 22.4 m/s

v = final speed = 0 m/s

a = acceleration = - 4.2 m/s²

d = stopping distance = ?

using the kinematics equation

v² = v₀² + 2 a d

0² = 22.4² + 2 ( - 4.2) d

d = 60 m