During the braking of a car weighing 2000 kg, its speed decreased from 72 km / h to 0.

During the braking of a car weighing 2000 kg, its speed decreased from 72 km / h to 0. How long did the braking last if the braking force was 8000 N?

According to Newton’s second law:
F = m * a, where F is the braking force (F = 8000 N), m is the mass of the car (m = 2000 kg), and is the acceleration of the car (m / s²).
Let’s express and calculate the acceleration of the car:
a = F / m = 8000/2000 = 4 m / s².
The braking time is calculated from the formula:
t = (V – V0) / a, where V is the final vehicle speed (V = 0 m / s), V0 is the initial vehicle speed (V0 = 72 km / h = 72 * 1000/3600 = 20 m / s).
t = (V – V0) / a = 20/4 = 5 s.
Answer: The braking time is 5 seconds.