A 1200.0-kg car is traveling at 19m/s. The driver suddenly slams on the brakes and skids to a stop. The coefficient of kinetic friction between the tires and the road is 0.80. For what length of time is the car skidding?

1.7 s

2.9 s

3.9 s

2.4 s

Answer

option D)

2.4 seconds

Explanation

Given in the question,

mass of car = 1200kg

speed of car = 19m/s

Force due to direction of travel

F = ma

= 12000 (a)

Force to due frictional force in reverse direction

-F = mg (friction coefficient)

= - 12000 (9.81) (0.8)

-mg (friction coefficient) = ma

(cancelling mass from both side of equation)

g (0.8) = a

(9.81) (0.8) = a

a = 7.848 m/s²

Use Newton Law of motionvf - vo = a • t

where vf = final velocity

vo = initial velocity

a = acceleration

t = time

0 - 19 = 7.8 (t)

t = 19/7.8

= 2.436 s

≈ 2.4s