Exam 6: Dynamics I: Motion Along a Line

A block is given a very brief push up a 20.0° frictionless incline to give it an initial speed of 12.0 m/s. (a) How far along the surface of the plane does the block slide before coming to rest? (b) How much time does it take to return to its starting position?

A factory robot drops a 10 kg computer onto a conveyor belt running at 3.1 m/s. The materials are such that μ_s = 0.50 and μ_k = 0.30 between the belt and the computer. How far is the computer dragged before it is riding smoothly on the belt?

A driver in a car traveling at slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the horizontal road is 0.80, how long will the skid marks be?

A 50.0-N box is sliding on a rough horizontal floor, and the only horizontal force acting on it is friction. You observe that at one instant the box is sliding to the right at 1.75 m/s and that it stops in 2.25 s with uniform acceleration. What magnitude force does friction exert on this box?

A person is dragging a packing crate of mass 100 kg across a rough horizontal floor where the coefficient of kinetic friction is 0.400. He exerts a force F sufficient to accelerate the crate forward. At what angle above horizontal should his pulling force be directed in order to achieve the maximum acceleration?

A traffic light weighing 100 N is supported by two ropes as shown in the figure. The tensions in the ropes are closest to

A fish weighing 16 N is weighed using two spring scales, each of negligible weight, as shown in the figure. What will be the readings of the scales?

A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15° above the horizontal. If T is the tension in this wire, then

In the figure, a block of mass M hangs at rest. The rope that is fastened to the wall is horizontal and has a tension off 52 N. The rope that is fastened to the ceiling has a tension of and makes an angle θ with the ceiling. What is the angle θ?

A block is on a frictionless horizontal table, on earth. This block accelerates at 3.6 m/ when a horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/ . A horizontal force of 45 N is applied to the block when it is on the moon. What acceleration does this force impart to the block?

You push downward on a box at an angle 25° below the horizontal with a force of 750 N. If the box is on a flat horizontal surface for which the coefficient of static friction with the box is 0.76, what is the mass of the heaviest box you will be able to move?

A box of mass 50 kg is at rest on a horizontal frictionless surface. A constant horizontal force F then acts on the box and accelerates it to the right. It is observed that it takes the box 6.9 seconds to travel 28 meters. What is the magnitude of the force?

15) Bumpers on cars are not of much use in a collision. To see why, calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm when the car had an initial speed of 2.0 m/s (about 4.5 mph). (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.)

In the figure, a T-bar ski tow pulls a skier up a hill inclined at 10° above horizontal. The skier starts from rest and is pulled by a cable that exerts a tension T at an angle of 30° above the surface of the hill. The mass of the skier is 60 kg and the effective coefficient of kinetic friction between the skis and the snow is 0.100. What is the maximum tension in the cable if the starting acceleration is not to exceed 0.400 g?

A block is on a frictionless horizontal table, on earth. This block accelerates at 1.9 m/ when a horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/s². What is the weight of the block on the moon?

When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal speed. Once he has reached terminal speed

In a shuffleboard game, the puck slides a total of before coming to rest. If the coefficient of kinetic friction between the puck and the horizontal board is 0.28, what was the initial speed of the puck?

A 60.0-kg person rides in an elevator while standing on a scale. The scale reads 400 N. The acceleration of the elevator is closest to

A box slides down a frictionless plane inclined at an angle θ above the horizontal. The gravitational force on the box is directed

Two objects, each of weight W, hang vertically by spring scales as shown in the figure. The pulleys and the strings attached to the objects have negligible weight, and there is no appreciable friction in the pulleys. The reading in each scale is