Beth was driving north on Hwy 75 with a speed of 40.4 m/s when she heard on a CB
ID: 1333671 • Letter: B
Question
Beth was driving north on Hwy 75 with a speed of 40.4 m/s when she heard on a CB that a patrolman was hiding 106.6 m north of where she is. Knowing that the patrolman can start clocking the car in 3.4 seconds, Beth decided to slow to 27.3 m/s. and immediately pressed on the brakes. Assume that the overall mass of the car with its occupants is 1102 kg and that the acceleration of the car while it is slowing is -3.9 m/s2.
a) What is in Newtons the net force acting on the car while it is slowing down? (don't include units in your answer and use North as the positive direction)
b) What is in Newtons the total weight of the car while it is slowing down? (don't include units in your answer, use North and up as positive directions, and 10 N/kg for g)
c) What is in Newtons the friction force acting on the car while it is slowing down? (don't include units in your answer and use North as the positive direction)
d) What is in Newtons the Normal force acting on the car while it is slowing down? (don't include units in your answer, use North and up as positive directions, and use 10 N/kg for g)
Explanation / Answer
a)
here
F = m * a
F = 1102 * -3.9
F = 4297.8 N
b)
W = 1102 * 9.8
W = 10799.6 N
downward
c)
the friction force
4297.8 = 10799.6 * u
u = 0.398
then
Ffriction = 1102 * 3.9 * 0.398 = 1710.34 N
d)
F = m * g
F = 1102 * 9.8
F = 10799.6 N
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