Exam 5: Applying Newtons Laws

Equilibrium: The figure shows a 2000 kg cable car descending a high hill. A counterweight of mass 1800 kg on the other side of the hill aids the brakes in controlling the cable car's speed. The rolling friction of both the cable car and the counterweight are negligible. How much braking force does the cable car need to descend at constant speed?

Banked curves: Suppose a highway curve is properly banked to eliminate friction for a speed of 45 km/h. If your tires were bald and you wanted to avoid sliding on the road, you would have to drive

Slanted surfaces with friction: A box is sliding down an incline tilted at a 12.0° angle above horizontal. The box is initially sliding down the incline at a speed of 1.50 m/s. The coefficient of kinetic friction between the box and the incline is 0.340. How far does the box slide down the incline before coming to rest?

Banked curves: A 600-kg car traveling at 30.0 m/s is going around a curve having a radius of 120 m that is banked at an angle of 25.0°. The coefficient of static friction between the car's tires and the road is 0.300. What is the magnitude of the force exerted by friction on the car?

Multiple-object systems without friction: The figure shows a 100-kg block being released from rest from a height of 1.0 m. It then takes it 0.90 s to reach the floor. What is the mass m of the other block? The pulley has no appreciable mass or friction.

Newton's second law: On its own, a certain tow-truck has a maximum acceleration of 3.0 m/s². What would be the maximum acceleration when this truck was towing a bus of twice its own mass?

General questions: Consider what happens when you jump up in the air. Which of the following is the most accurate statement?

Uniform circular motion: If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out because an outward force balances the pull of gravity on the water.

General questions: In order to lift a bucket of concrete, you must pull up harder on the bucket than it pulls down on you.

Air resistance: An object weighing 4.00 N falls from rest subject to a frictional drag force given by F_drag = bv², where v is the speed of the object and b = 3.00 N ∙ s²/m². What terminal speed will this object approach?

Multiple-object systems with friction: Three objects are connected as shown in the figure. The strings and frictionless pulleys have negligible masses, and the coefficient of kinetic friction between the 2.0-kg block and the table is 0.25. What is the acceleration of the 2.0-kg block?

Banked curves: Engineers are designing a curved section of a highway. If the radius of curvature of the curve is at what angle should the curve be banked so that a car traveling at 29.0 m/s will stay on the road without the aid of frictional forces?

Slanted surfaces without friction: A system comprising blocks, a light frictionless pulley, a frictionless incline, and connecting ropes is shown in the figure. The 9.0-kg block accelerates downward when the system is released from rest. The tension in the rope connecting the 6.0-kg block and the 4.0-kg block is closest to

Newton's second law: A 7.0-kg object is acted on by two forces. One of the forces is 10.0 N acting toward the east. Which of the following forces is the other force if the acceleration of the object is 1.0 m/s² toward the east?

Slanted surfaces with friction: A brick is resting on a rough incline as shown in the figure. The friction force acting on the brick, along the incline, is

General questions: An object is moving to the right, and experiencing a net force that is directed to the right. The magnitude of the force is decreasing with time. The speed of the object is

Multiple-object systems without friction: Three boxes in contact rest side-by-side on a smooth, horizontal floor. Their masses are 5.0-kg, 3.0-kg, and 2.0-kg, with the 3.0-kg box in the center. A force of 50 N pushes on the 5.0-kg box, which pushes against the other two boxes. (a) Draw the free-body diagrams for each of the boxes. (b) What magnitude force does the 3.0-kg box exert on the 5.0-kg box? (c) What magnitude force does the 3.0-kg box exert on the 2.0-kg box?

Uniform circular motion: The figure shows two wires that are tied to a 710 g mass that revolves in a horizontal circle at a constant speed of 7.5 m/s. What is the tension in the upper wire?

General questions: A ball is tossed vertically upward. When it reaches its highest point (before falling back downward)

Equilibrium: Two blocks are connected by a string that goes over an ideal pulley as shown in the figure and pulls on block A parallel to the surface of the plane. Block A has a mass of 3.00 kg and can slide along a rough plane inclined 30.0° to the horizontal. The coefficient of static friction between block A and the plane is 0.400. What mass should block B have in order to start block A sliding up the plane?