A desperate hiker has to think fast to help his friend who has fallen below him. Quickly, he ties a rope to a rock of mass ma and makes his way over the ledge (see the figure). If the coefficient of maximum static friction between the rock and the ground is µ, and the mass of the hiker is mg, what is the maximum mass of the friend, mc, that the rock can hold so the hikers can then make their way up over the ledge? Assume the rope is parallel to the ground and the point where the rope passes over the ledge is frictionless. mc = Ju

Santa Claus tries to drag his bag of presents along a horizontal surface by a red rope that is angled at 55 degrees above the horizontal. Santa Claus applies a force due to tension of 4500N along the red rope. This is the minimum force to just start the bag in motion. The coefficient of kinetic friction between the bag and the ground is 0.3 and the coefficient of static friction is 0.5. What is the mass of the bag?

A truck with a mass of 750 kg is traveling along a wet road at 30.0 m/s  The driver slams on the brakes and skids to a stop.  If the coefficient of kinetic friction between the tires and the road is 0.50: what frictional force stops the truck? how far does it skid?

You are a bully.  You pin a 48 kg dweeb to a wall so that his feet aren't touching the ground.  Your arm is extended so that it makes an angle 28 degrees with the horizontal.  The dweeb's back is so sweaty with fear that there is no friction between his back and the wall.  What is the magnitude of the force , in N, you must apply to keep the dweeb in equilibrium? (Use g = 10 m/s2) This scenario is represented schematically below.  Unfortunately for you, years later the dweeb is your boss and he makes your life miserable. (Please answer to the fourth decimal place - i.e 12.3445)

A rock rests on a horizontal plane. The plane is slowly tilted so that the angle between the surface and the horizontal increases to 20 degrees, at which point the rock is about to slip. What is the coefficient of static friction between the rock and the surface, to two significant figures? O 0.36 2.2 3.4 9.4 O 13 O

Two crates of fruit  are released from the top of a ramp inclined at 30 degrees from the horizontal and 4.5 meter long. The two crates consist of  an apple crate of mass 20 kg that is placed in front of a watermelon crate of mass 80 kg.  The apple crate has a coefficient of friction of 0.20 while the watermelon crate has a coefficient of friction of 0.15. How long does it take the apple crate to reach the bottom of the incline if it needs to travel a distance of 4.5 meters?

A 40 N box is resting on a table when a 20 N force is applied to it horizontally. The coefficients of static and kinetic friction are 0.3 and 0.1, respectively. Which of the following best describes the resulting motion of the box?    The motion of the box cannot be determined with the given information.      The box accelerates in the direction of the applied force.      The box remains at rest.      The box moves with a constant velocity in the direction of the applied force.

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 hunter is pulling his sled 44 kg in mass behind him on snow. He exerts a pull of 100 N in magnitude and at 20 degrees above the horizontal to ensure he could move at a constant speed through the snow-covered land. What is the coefficient of friction between the sled and the snow?

A stationary 10kg object is sitting on the ground. The coefficient of static friction between the object and the ground is 0.8 and the coefficient of kinetic friction is 0.6. How much horizontal force needs to be applied in order to make the object move?