Friction Review
1. Indiana Jones is lecturing to his class while standing at the front of the classroom. What is the
normal force acting on Indiana Jones, who has a mass of 75 kg?
2. At the museum, Jones moves a 175 kg statue across the floor by pushing horizontally with a
force of 700 N. The statue moves with a constant velocity.
a. What is the normal force on the statue?
b. What is the kinetic friction force acting on the statue?
c. What is the coefficient of kinetic friction?
3. While trying to save his father from the Nazis, Indiana Jones is captured and tied to a chair.
Both he and the chair have a combined mass of 185 kg. The Nazi, Colonel Vogel, moves
Jones to the other side of the room by pushing with a horizontal force of 550 N to set it in
motion. Once the chair is in motion, a 520 N horizontal force keeps it moving at a constant
velocity.
a. Find the coefficient of static friction between the chair and the floor.
b. Find the coefficient of kinetic friction between the chair and the floor.
4. Unhappy with another artifact’s location, Jones moves the artifact to a new location. He
pushes downward at an angle of 30o below the horizontal on the 55 kg artifact with a force of
250 N. The artifact moves with a constant velocity.
a. What is the normal force on the artifact?
b. What is the kinetic friction force acting on the artifact?
c. What is the coefficient of kinetic friction?
5. While recovering the Cross of Coronado, Jones rests the 4.5 kg cross on an incline of angle 50o.
a. Find the normal force of the incline on the Cross of Coronado.
b. Find the static friction preventing the Cross of Coronado from sliding down the
incline.
6. During another adventure, Jones rests the Crystal Skull on a ramp, but it begins to slide
down. The coefficient of static friction between the 5 kg Crystal Skull and the 25o incline is
0.34. What is the minimum force that must be applied to the Crystal Skull perpendicular to
the incline to prevent it from sliding down?
F
25o