- #1
Joyci116
- 45
- 0
Homework Statement
Your 3.80-kg physics book is next to you on the horizontal seat of your car. The coefficient of static friction between the book and the seat is 0.650, and the coefficient of kinetic friction is 0.550. Suppose you are traveling at 72 km/h=20.0m/s and brake to a stop over a distance of 45.0m. (a)Will the book start to slide over the seat? (b)What force does the seat exert on the book in the process?
Homework Equations
F=[itex]\mu[/itex]N
F=max
N=mg=may
The Attempt at a Solution
I know:
m=3.80kg
[itex]\mu[/itex]s=0.650
[itex]\mu[/itex]k=0.550
Vi=72.0 km/h=20.0m/s
Vf=0
x=45.0m
Well, coefficient of static friction means stationary and coefficient of kinetic friction means moving. Since in this case [itex]\mu[/itex]s>[itex]\mu[/itex]k, that means that the book is stationary.
So part a is no, because the static friction is greater than the kinetic friction.
But I had trouble with part b. I drew a free-body diagram. I have the weight force(earth,book) pointing down, normal force(earth,book) pointing up, and friction force point to the left. I have the weight force and normal force the same length, but the friction force is shorter. I don't know what to do after that. It asks for the force that the seat exert on the book, so would that be a normal force that the car seat might exert on the book?
Thank you,
Joyce