Question

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

Answer 1

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

Step-by-step 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 =
`(7.83* 10^3)/(1.20* 10^3)`

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