Use the values from PRACTICE IT to help you work this exercise. A police investigator measures straight skid marks 20.0 m long in an accident investigation. Assuming a friction force and car mass the same as in the problem above, what was the minimum speed of the car when the brakes locked

minimum speed of the car when the brakes locked is 16.15 m/s

Explanation:

given data

straight skid marks = 20.0 m

solution

we consider here mass of car is 1.20 ×  10³ kg  

and friction force is 7.83× 10³ N

so here acceleration will be

acceleration = force ÷ mass   ................1

acceleration =  

acceleration = 6.525 m/s²  

and

speed after 20  m final speed v is 0 m/s

and here minimum speed of the car when brakes was locked  is u m/s

so we apply equation of motion

v² - u² = 2 × a × s    ............2

0 - u² = 2 × 6.525  × 20    

solve it we get

u = 16.15 m/s

so minimum speed of the car when the brakes locked is 16.15 m/s