64 Two horizontal forces are applied to a 2.0-kilogram block on a frictionless, horizontal surface, as shown in the following diagram. 20N F 8.0N 2.0 kg Frictionless horizontal surface The acceleration of the block is (1) 5.0 m/s to the right (2) 5.0 m/s to the left (3) 3.0 m/sto the right (4) 3.0 m/s to the left

64 Two horizontal forces are applied to a 2.0-kilogram block on a frictionless, horizontal surface, as shown in the following diagram. 20N F 8.0N 2.0 kg Frictionless horizontal surface The acceleration of the block is (1) 5.0 m/s to the right (2) 5.0 m/s to the left (3) 3.0 m/sto the right (4) 3.0 m/s to the left

College Physics

10th Edition

ISBN:9781285737027

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter4: The Laws Of Motion

Section: Chapter Questions

Problem 7WUE: Calculate the normal force on a 15.0 kg block in the following circumstances: (a) The block is...

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An airplane of mass 1.50 104 kg is in level flight, initially moving at 60.0 m/s. The resistive force exerted by air on the airplane has a magnitude of 4.0 104 N. By Newtons third law, if the engines exert a force on the exhaust gases to expel them out of the back of the engine, the exhaust gases exert a force on the engines in the direction of the airplanes travel. This force is called thrust, and the value of the thrust in this situation is 7.50 104 N. (a) Is the work done by the exhaust gases on the airplane during some time interval equal to the change in the airplanes kinetic energy? Explain. (b) Find the speed of the airplane after it has traveled 5.0 102 m.
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In Example 5.7, we pushed on two blocks on a table. Suppose three blocks are in contact with one another on a frictionless, horizontal surface as shown in Figure P5.43. A horizontal force F is applied to m1. Take m1 = 2.00 kg, m2 = 3.00 kg, m3 = 4.00 kg, and F = 18.0 N. (a) Draw a separate free-body diagram for each block. (b) Determine the acceleration of the blocks. (c) Find the resultant force on each block. (d) Find the magnitudes of the contact forces between the blocks. (e) You are working on a construction project. A coworker is nailing up plasterboard on one side of a light partition, and you are on the opposite side, providing backing by leaning against the wall with your back pushing on it. Every hammer blow makes your back sting. The supervisor helps you put a heavy block of wood between the wall and your back. Using the situation analyzed in parts (a) through (d) as a model, explain how this change works to make your job more comfortable.
Review. A magician pulls a tablecloth from under a 200-g mug located 30.0 cm from the edge of the cloth. The cloth exerts a friction force of 0.100 N on the mug, and the cloth is pulled with a constant acceleration of 3.00 m/s2. How far does the mug move relative to the horizontal tabletop before the cloth is completely out from under it? Note that the cloth must move more than 30 cm relative to the tabletop during the process.
A 15.0-lb block rests on a horizontal floor, (a) What force does the floor exert on the block? (b) A rope is tied to the block and is run vertically over a pulley. The other end is attached to a free-hanging 10.0-lb object. What now is the force exerted by the floor on the 15.0-lb block? (c) If the 10.0-lb object in part (b) is replaced with a 20.0-lb object, what is the force exerted by the floor on the 15.0-lb block?
A magician pulls a tablecloth from under a 200-g mug located 30.0 cm from the edge of the cloth. The cloth exerts a friction force of 0.100 N on the mug and is pulled with a constant acceleration of 3.00 m/s2. How far does the mug move relative to the horizontal tabletop before the cloth is completely out from under it? Note that the cloth must move more than 30 cm relative to the tabletop during the process.
Calculate the normal force on a 15.0 kg block in the following circumstances: (a) The block is resting on a level surface. (b) The block is resting on a surface tilted up at a 30.0 angle with respect to the horizontal. (c) The block is resting on the floor of an elevator that is accelerating upwards at 3.00 m./s2. (d) The block is on a level surface and a force of 125 N is exerted on it at an angle of 30.0 above the horizontal. (Sec Section 1.5.)
Two teams of nine members each engage in a 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? (b) What is the tension in the section of rope between the teams?
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Assume the resistive force acting on a speed skater is proportional to the square of the skaters speed v and is given by f = kmv2, where k is a constant and m is the skaters mass. The skater crosses the finish line of a straight-line race with speed vi and then slows down by coasting on his skates. Show that the skaters speed at any time t after crossing the finish line is v(t) = vi/(1 + ktvi).
An inventive child wants to reach an apple in a tree without climbing the tree. Sitting in a chair connected to a rope that passes over a frictionless pulley (Fig. P4.88), the child pulls on the loose end of the rope with such a force that the spring scale reads 250 N. The childs true weight is 320- N, and the chair weighs 160 N. The childs feet are not touching the ground. (a) Show that the acceleration of the system is upward, and find its magnitude. (b) Find the force the child exerts on the chair. Figure P4.88
A block of ice (m = 15.0 kg) with an attached rope is at rest on a frictionless surface. You pull the block with a horizontal force of 95.0 N for 1.54 s. a. Determine the magnitude of each force acting on the block of ice while you are pulling. b. With what speed is the ice moving after you are finished pulling? Repeat Problem 71, but this time you pull on the block at an angle of 20.0.