Exam 5: Applying Newtons Laws

Newton's second law: The figure shows a graph of the acceleration of a 125-g object as a function of the net force acting on it. What is the acceleration at points A and B?

Multiple-object systems without friction: Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure. The tension in the wire connecting the 10.0-kg and 15.0-kg objects is measured to be 133 N. What is the tension in wire A?

Multiple-object systems without friction: Two objects are connected by a very light flexible string as shown in the figure, where M = 0.60 kg and m = 0.40 kg. You can ignore friction and the mass of the pulley. (a) Draw free-body diagrams for each object. (b) Calculate the magnitude of the acceleration of each object. (c) Calculate the tension in the string.

Multiple-object systems without friction: A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface as shown in the figure. The 6.00-kg block is being pushed by a horizontal 20.0-N force as shown. What is the magnitude of the force that the 6.00-kg block exerts on the 4.00-kg block?

Multiple-object systems with friction: A rope pulls on the lower block in the figure with a tension force of 20 N. The coefficient of kinetic friction between the lower block and the surface is 0.16. The coefficient of kinetic friction between the lower block and the upper block is also 0.16. The pulley has no appreciable mass or friction. What is the acceleration of the 2.0 kg block?

Friction: 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?

Equilibrium: Block A of mass 8.0 kg and block X are attached to a rope that passes over a pulley. A 50-N force P is applied horizontally to block A, keeping it in contact with a rough vertical face. The coefficients of static and kinetic friction between the wall and block A are μ_s = 0.40 and μ_k = 0.30. The pulley is light and frictionless. In the figure, the mass of block X is adjusted until block A descends at constant velocity of 4.75 cm/s when it is set into motion. What is the mass of block X?

Newton's second law: The graph in the figure shows the net force acting on a 3.0-kg object as a function of time. (a) What is the acceleration of this object at time t = 2.0 s? (b) Draw, to scale, a graph of the acceleration of this object as a function of time over the range t = 0.00 s to t = 7.0 s.

Slanted surfaces without friction: A child on a sled starts from rest at the top of a 15° slope. If the trip to the bottom takes how long is the slope? Assume that frictional forces may be neglected.

Newton's second law: The figure shows a graph of the acceleration of an object as a function of the net force acting on it. The mass of this object, in grams, is closest to

Newton's second law: 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

Newton's second law: The figure shows an acceleration-versus-force graph for three objects pulled by rubber bands. The mass of object 2 is 36 kg. What are the masses of objects 1 and 3?

Slanted surfaces with friction: A 250-kg crate is on a rough ramp, inclined at 30° above the horizontal. The coefficient of kinetic friction between the crate and ramp is 0.22. A horizontal force of 5000 N is applied to the crate, pushing it up the ramp. What is the acceleration of the crate?

General questions: A stalled car is being pushed up a hill at constant velocity by three people. The net force on the car is

Equilibrium: 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 of 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?

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

Friction: Jason takes off from rest across level water on his jet-powered skis. The combined mass of Jason and his skis is 75 kg (the mass of the fuel is negligible). The skis have a thrust of 200 N and a coefficient of kinetic friction on water of 0.10. Unfortunately, the skis run out of fuel after only 48 s. What is Jason's top speed?

General questions: Which one of the following free-body diagrams best represents the free-body diagram, with correct relative force magnitudes, of a person in an elevator that is traveling upward but is gradually slowing down at a rate of 9 m/s2? _f is the force of the floor on the person and _g is the force of gravity on the person.

General questions: In order to get an object moving, you must push harder on it than it pushes back on you.