Friction LT3 Practice Problems
Learning Target
3) I can utilize the coefficients of static and kinetic friction to solve motion
problems.
1. A girl exerts a 36-N horizontal force as she pulls a 52N sled across a
cement sidewalk at constant speed. What is the coefficient of kinetic
friction between the sidewalk and the metal sled runners? Ignore air
resistance.
2. You need to move a 105kg sofa to a difference location in the room. It
takes a force of 102N to start it moving. What is the coefficient of
static friction between the sofa and the carpet?
3. Mr. Ames is dragging a box full of books from his office to his car.
The box and books together have a combined weight of 134 N. If the
coefficient of static friction is between the pavement and box is 0.55,
how hard must Mr. Ames push the box in order to get it to start
moving?
4. A sled sits on packed snow. The coefficient of kinetic friction is 0.12.
If a person and the sled together weigh 650N, what force is needed to
pull the sled across the snow at constant speed?
5. A 1.4kg block slides across a rough surface such that is slows down
with an acceleration of 1.25m/s2. What is the coefficient of kinetic
friction between the block and the surface?
6. You help your mom move a 41kg bookcase. If you push with a force of
65N and the bookcase accelerates at 0.12m/s2, what is the coefficient
of kinetic friction between the bookcase and the carpet?
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7. Martha is driving along on a rainy night at 23m/s when she sees a tree
branch lying across the road and slams on the brakes when the branch
is 60.0m in front of her. If the coefficient of kinetic friction between
the car’s locked tires and the road is 0.41, will the car stop before
hitting the branch? The mass of the car with Martha is 2400kg.
8. Stacie, who has a mass of 45kg, starts down a slide that has an angle
of 45º with the horizontal. If the coefficient of kinetic friction
between Stacie’s shorts and the slide is 0.25, what is her acceleration?
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