## Friday, 12 September 2014

### FRICTION 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. Anil 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. Anil 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?

7.       Smitha  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 smitha is 2400kg.