Question
You are driving at the speed of 33.4 m/s
(74.7296 mph) when suddenly the car in
front of you (previously traveling at the same speed) brakes. Considering an average human reaction, you press your brakes 0.484 s later. Assume that the brakes on both cars are fully
engaged and that the coefficient of friction is 0.92 between both cars 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.
(74.7296 mph) when suddenly the car in
front of you (previously traveling at the same speed) brakes. Considering an average human reaction, you press your brakes 0.484 s later. Assume that the brakes on both cars are fully
engaged and that the coefficient of friction is 0.92 between both cars 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.
Answers
drwls
This problemn contains more information than necessary to answer the question. It may be they are trying to confuse you. Or uou may need the extra information in a followup question about whether you hit the car or not.
The deceleration of the car in front has nothing to do with your car or reaction time. It is
a = -F/m,
where F is the friction force and m is the mass. The minus sign indicates deceleration.
Although they do not tell you the mass, it will cancel out of the equation when you write
F = 0.92 m g
Thus a = -0.92 g
The deceleration of the car in front has nothing to do with your car or reaction time. It is
a = -F/m,
where F is the friction force and m is the mass. The minus sign indicates deceleration.
Although they do not tell you the mass, it will cancel out of the equation when you write
F = 0.92 m g
Thus a = -0.92 g