6.23 K) 7of 18 Part A At an accident scene on a level road, investigators measur

Question

6.23 K) 7of 18 Part A At an accident scene on a level road, investigators measure a cars skid mark to be 89 m long It was Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes estimated to be 0.33 Express your answer to two significant figures and include the appropriate units. Part B Since both the change in kinetic energy and the work done by friction are proportional to the mass, The mass cancels out of the equation O Since the change in kinetic energy and the work done by friction do not depend on mass Since the work done by friction does not depend on mass

Explanation / Answer

Part a)

Here final speed of car, v = 0

Coefficient of friction, = 0.33

we neet to find initial velocity of car when brakes were applied

let initial velocity = u

and net acceleration of car = a

Work done on the car for distance d = car's K.E. = 0.5mu^2

F.d = 0.5mu^2

ma.d = 0.5mu^2

here a = g

u^2 = 2*g*d = 2*0.33*9.8*89 = 575.65

Thus initial velocity of car when brakes were applied , u = 23.99 m/s ~ 24m/s

Part b)

3rd option is correct one

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