Question

During a cold winter night a car unfortunately skids to a stop shortly before crashing into a donut shop. The skid marks are 34.0m long and the car has a mass of 825kg. From a measurement made at the time of the incident, the coeff. of friction was determined to be 0.300 How fast was the car going when the driver applied the brakes (assume that the brakes are the only resistive force that stops the vehicle)?

Answer 1

Answer: The car was moving with the speed of 14.13 m/s.

Explanation:

Length of the skid marks,d = 34 m

Mass of the car = 825 kg

Coefficient of friction = $\mu =0.300$

Velocity of the car after applying the brakes =v

Acceleration due gravity = $9.8 m/s^2$

$d=\frac{v^2}{2\mu g}$

$34 m=\frac{v^2}{2\times 0.300\times 9.8 m/s^2}$

$v^2=34 m\times 2\times 0.300\times 9.8 m/s^2=199.92 m^2/s^2$

v = 14.13 m/s

The car was moving with the speed of 14.13 m/s.