Two boxes are connected by a weightless cord running over a very light frictionless pulley as shown in the figure. Box A, of mass 8.0 kg, is initially at rest on the top of a horizontal table. The coefficient of kinetic friction between box A and the table is 0.20. Box B has a mass of 15.0 kg, and the system begins to move just after it is released. a) Draw the free-body diagrams for each of the boxes, identifying all of the forces acting on eạch one. b) Calculate the magnitude of the acceleration of each box. Use g = 9.8 m/s²

Two boxes are connected by a weightless cord running over a very light frictionless pulley as shown in the figure. Box A, of mass 8.0 kg, is initially at rest on the top of a horizontal table. The coefficient of kinetic friction between box A and the table is 0.20. Box B has a mass of 15.0 kg, and the system begins to move just after it is released. a) Draw the free-body diagrams for each of the boxes, identifying all of the forces acting on eạch one. b) Calculate the magnitude of the acceleration of each box. Use g = 9.8 m/s²

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter4: Dynamics: Force And Newton's Laws Of Motion

Section: Chapter Questions

Problem 35PE: A nurse pushes a cart by exerting a force on the handle at a downward angle 35.0° below the...

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Suppose two children push horizontally, but in exactly opposite directions, on a third child in a wagon. The first child exerts a force of 75.0 N, the second exerts a force of 90.0 N, friction is 12.0 N, and the mass of the third child plus wagon is 23.0 kg. (a) What is the system of interest if the acceleration of the child in the wagon is to be calculated? (See the free-body diagram.) (b) Calculate the acceleration. (c) What would the acceleration be if friction were 15.0 N?
Two teams of nine members each engage in tug-of-war. Each of the first team’s members has an average mass of 68 kg and exerts an average force of 1350 N horizontally. Each of the second team’s members has an average mass of 73 kg and exerts an average force of 1365 N horizontally. (a) What is magnitude of the acceleration of the two teams, and which team sins? (b) What is the tension in the section of rope between the teams?
Give reasons for the answers to each of the following questions: (a) Clan a normal force be horizontal? (b) Can a normal force be directed vertically downward? (c) Consider a tennis ball in contact with a stationary floor and with nothing else. Can the normal force be different in magnitude from the gravitational force exerted on the ball? (d) Can the force exerted by the floor on the hall be different in magnitude from the force the ball exerts on the floor?
Three objects are connected on a table as shown in Figure P5.14. The coefficient of kinetic friction between the block of mass m2 and the table is 0.350. The objects have masses of m1 = 4.00 kg, m2 = 1.00 kg, and m3 = 2.00 kg, and the pulleys are frictionless. (a) Draw a free-body diagram of each object. (b) Determine the acceleration of each object, including its direction. (c) Determine the tensions in the two cords. What If? (d) If the tabletop were smooth, would the tensions increase, decrease, or remain the same? Explain. Figure P5.14
A nurse pushes a cart by exerting a force on the handle at a downward angle 35.0° below the horizontal. The loaded cart has a mass of 28.0 kg, and the force of friction is 60.0 N. (a) Draw a free-body diagram for the system of interest. (b) What force must the nurse exert to move at a constant velocity?
Two blocks of masses m1 and m2 (m1 m2) are placed on a frictionless table in contact with each other. A horizontal force of magnitude F is applied to the block of mass m1 in Figure P4.62. (a) If P is the magnitude of the contact force between the blocks, draw the free-body diagrams for each block. (b) What is the net force on the system consisting of both blocks? (c) What is the net force acting on m1? (d) What is the net force acting on m2? (e) Write the x-component of Newtons second law for each block. (f) Solve the resulting system of two equations and two unknowns, expressing the acceleration a and contact force P in terms of the masses and force. (g) How would the answers change if the force had been applied to m2 instead? (Hint: use symmetry; dont calculate!) Is the contact force larger, smaller, or the same in this case? Why? Figure P4.62
Two blocks of masses m1 and m2 (m1 m2) are placed on a frictionless table in contact with each other. A horizontal force of magnitude F is applied to the block of mass m1 in Figure P4.62. (a) If P is the magnitude of the contact force between the blocks, draw the free-body diagrams for each block. (b) What is the net force on the system consisting of both blocks? (c) What is the net force acting on m1? (d) What is the net force acting on m2? (e) Write the x-component of Newtons second law for each block. (f) Solve the resulting system of two equations and two unknowns, expressing the acceleration a and contact force P in terms of the masses and force. (g) How would the answers change if the force had been applied to m2 instead? (Hint: use symmetry; dont calculate!) Is the contact force larger, smaller, or the same in this case? Why? Figure P4.62
A brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800 N on him. The mass of the losing player plus equipment is 90.0 kg, and he is accelerating at 1.20 m/s2 backward. (a) What is the force of friction between the losing player's feet and the grass? (b) What force does the winning player exert on the ground to move forward if his mass plus equipment is 110 kg? (c) Draw a sketch of the situation showing the system of interest used to solve each part. For this situation, draw a free-body diagram and write the net force equation.
A worker is attempting to lift a 55.0-kg palette of bricks resting on the ground by means of a rope attached to a pulley. a. Before the worker pulls on the rope, what is the force exerted by the ground on the palette? b. The worker exerts a force of 295 N downward on his end of the rope. What is the force exerted by the ground on the palette? c. If the worker doubles the downward force, what is the force exerted by the ground on the palette?
A block with mass m1 hangs from a rope that is extended over an ideal pulley and attached to a second block with mass m2 that sits on a ledge slanted at an angle of 20° (see figure below). Suppose the system of blocks is initially held motionless and, when released, begins to accelerate. If m1 = 7.25 kg, m2 = 2.25 kg, and the magnitude of the acceleration of the blocks is 0.150 m/s2, find the magnitude of the kinetic frictional force between the second block and the ledge. What is the value of the coefficient of kinetic friction between the block and the ledge?
Two blocks, M1 and M2, are connected by a massless string that passes over a massless pulley as shown in the figure. M2, which has a mass of 25.0 kg, rests on a long ramp of angle ?=25.0∘. Friction can be ignored in this problem. Determine the mass ?1 of block M1 for which the two blocks are in equilibrium (no acceleration). If the actual mass of M1 is 5.00 kg and the system is allowed to move, what is the acceleration ? of the two blocks? A positive acceleration corresponds to M2 moving up the incline. What distance ? does block M2 move in 2.00 s?
A light rope is attached to a block with mass 4.00 kg that rests on a frictionless,horizontal surface. The horizontal rope passes over a frictionless, massless pulley, and ablock with mass m is suspended from the other end. When the blocks are released, thetension in the rope is 10.0 N. (a) Draw two free-body diagrams, one for the 4.00-kg blockand one for the block with mass m. (b) What is the acceleration of either block? (c) Findthe mass m of the hanging block. (d) How does the tension compare to the weight of thehanging block?