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You are driving at the speed of 31 m/s
(69.3599 mph) when suddenly the car in
front of you (previously traveling at the same
speed) brakes and begins to slow down with
the largest deceleration possible without skidding. Considering an average human reaction,
you press your brakes 0.546 s later. You also
brake and decelerate as rapidly as possible
without skidding. Assume that the coefficient
of static friction is 0.925 between both cars’
wheels and the road.
The acceleration of gravity is 9.8 m/s2.
Calculate the acceleration of the car in front
of you when it brakes.
Answer in units of m/s2
2 answers
M*g = M*9.8 = 9.8M = Wt. of car.
Fp = 9.8M*sin 0 = 0 = Force parallel with surface.
Fn = 9.8M*Cos 0 = 9.8M = Normal force.
Fs = u*Fn = 0.925*9.8M = 9.1M. = Force of static friction.
Fp-Fs = M*a;
0-9.1M = M*a,
Divide both sides by M:
a = -9.1 m/s^2.
Fp = 9.8M*sin 0 = 0 = Force parallel with surface.
Fn = 9.8M*Cos 0 = 9.8M = Normal force.
Fs = u*Fn = 0.925*9.8M = 9.1M. = Force of static friction.
Fp-Fs = M*a;
0-9.1M = M*a,
Divide both sides by M:
a = -9.1 m/s^2.
1 answer