The driver turned off the car engine at a speed of 72 km / h. After 3.4 seconds the car stopped.

The driver turned off the car engine at a speed of 72 km / h. After 3.4 seconds the car stopped. The friction force of the wheels on the asphalt is 5880N. What is the weight of the car.

We find the mass of the car from Newton’s second law:
F = a * m;
m = F / a;
here a is the acceleration of deceleration:
V0 – V = a * t;
V0 = a * t, since the final speed is V = 0.
a = V0 / t;
m = F * t / V0;
V0 = 72km / h = 20m / s;
m = 5880 * 3.4 / 20 = 999.6kg.