A man standing on the ground exerts a horizontal force of 439 N when pushing on his friend standing on the skateboard. If the friend’s mass is 70 kg, the skateboard’s mass is 2 kg, and the coefficient of static friction between the friend’s feet and the skateboard is 0.8, calculate the magnitude of the force of static friction between the skateboard and the friend’s feet. You can assume that the wheels on the skateboard are good enough so that you can neglect friction between the wheels and the ground

A box with a mass of 0.5 slugs lies on an inclined plane making an angle of 30o with the horizontal.  If the coefficient of kinetic friction between the box and the plane is 0.4, what is the magnitude of the force that must be applied parallel to the incline to keep the box moving down the incline at a constant speed?

A coin placed 29.6 cm from the center of a rotating, horizontal turntable slips when its speed is 51.6 cm/s.   What is the coefficient of static friction between coin and turntable?

A 7.5 kg backpack is sliding across the floor.  The coefficient of friction between the backpack and the floor is 0.20.  Answer the following:   Is this static or kinetic friction?

F 0 EC FAC $ Ed and Al are pushing on a couch as shown in the picture and it doesn't slip. Ed is pushing with a force of 198.9 N at an angle of 0 = 54 degrees with respect to the vertical and Al is pushing with a force of 60.2 N at an angle of = 35.4 degrees with respect to the horizontal. If the couch has a mass of 83 kg and the coefficients of static and kinetic friction between the couch and the floor are μg = 0.53, and k = 0.39, what is the magnitude of the force of friction exerted by the floor on the couch? Click here for a hint F

A contestant in a winter games event pushes a 59.0 kg block of ice across a frozen lake with a rope over his shoulder as shown in the figure. The coefficient of static friction is 0.1 and the coefficient of the the kinetic friction is 0.03. What is the minimum force (in N) he must exert to get the block moving?

A rope exerts a force of 50 N on a box to keep it stationary. If the box is on a plane inclined 25° from the horizontal and the coefficient of static friction is 0.29, calculate the normal force exerted on the box.

A 26.8 kg box sits on a ramp at an angle of 13° above the horizontal. If the coefficient of static friction between the box on the ramp is 0.215, what minimum applied force is required to keep the box at rest?

A block of mass 1.45 kg is resting on a board with friction.The board is inclined until the mass just starts to slide.  If the angle of the incline when the mass just barely begins to slide is 17.5 degrees,what is the coefficient of static friction between the block and the board?

At a construction site, a pallet of bricks is to be suspended by attaching a rope to it and connecting the other end to a couple of heavy crates on the roof of a building, as shown in (Figure 1). The rope pulls horizontally on the lower crate, and the coefficient of static friction between the lower crate and the roof is 0.509. What is the weight of the heaviest pallet of bricks that can be supported this way? (Hint: Start by drawing appropriate free-body diagrams.) (Express your answer in pounds.) What is the friction force on the upper crate under the conditions given in Part 1? (Express your answer in pounds.)