Friction Force & Direction for 925 kg Car at -12.2m/s2 Acceleration

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In summary, the conversation discusses finding the frictional force and direction of a breaking car with an average rate of acceleration of -12.2m/s2 and a mass of 925 kg. The frictional force can be found by multiplying the coefficient of friction with the normal force, which is equivalent to the car's weight. The conversation also suggests drawing a free-body diagram to determine the forces contributing to the acceleration.
  • #1
drinkingstraw
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The average rate of acceleration for a breaking car was -12.2m/s2. If the car had a mass of 925 kg, find the frictional force and direction.

a = -12.2m/s2
m = 925 kg
Fn = 9074.25 N

This is what I've figured out. I don't know how to find the coefficient of friction. If I get the coefficient I think I can multiply it by the normal force to get the frictional force.
 
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  • #2
You're complicating the problem unnecessarily.

The question asks only for the frictional force and direction. Try drawing a free-body diagram for the car and then write down the F=ma equations.
 
  • #3
F_f = u*F_n

F_n = mgF_f = u *mg

find u
 
  • #4
The problem only asks for F_f :smile:
The free body diagram is the way to go. Fn and Fg cancel out. What other force or forces provide the acceleration?
 

What is friction force?

Friction force is the force that opposes the relative motion between two surfaces in contact. It is caused by microscopic irregularities on the surfaces and acts in the direction opposite to the direction of motion.

How is friction force calculated?

The magnitude of friction force can be calculated by multiplying the coefficient of friction (a dimensionless value dependent on the nature of the surfaces) by the normal force (the force exerted by one surface on the other perpendicular to their contact).

What is the direction of friction force?

The direction of friction force is always opposite to the direction of motion or the applied force. In the case of a car accelerating at -12.2m/s2, the friction force would act in the direction opposite to the acceleration, in this case, towards the front of the car.

How does friction force affect the motion of a car?

Friction force plays a crucial role in the motion of a car. It is the force that allows the car to maintain traction and grip on the ground, preventing it from slipping or sliding. The friction force between the tires and the road also helps in slowing down or stopping the car when the brakes are applied.

Can friction force be reduced or eliminated?

Friction force can be reduced by using lubricants or smoother surfaces. However, it cannot be completely eliminated as it is a fundamental force in nature. In fact, friction force is necessary for many everyday tasks, such as walking, driving, and writing.

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