Concept explainers
Videos
Compare the net force on a heavy trunk when it’s (a) at rest on the floor; (b) being slid across the floor at constant speed; (c) being pulled upward in an elevator whose cable tension equals the combined weight of the elevator and trunk; and (d) sliding down a frictionless ramp.
(a)
The net force on a heavy trunk when it is at rest on the floor.
Answer to Problem 1FTD
The net force on a heavy trunk when it is at rest on the floor is zero.
Explanation of Solution
According to Newton’s first law of motion a body will remain in rest until it is acted upon by external unbalanced force. Therefore the net force acting on a body at rest is zero.
The forces acting on a body are weight of the body which is down ward and normal reaction which is upward. For a body at rest on the floor therefore the normal reaction will be equal to that of weight of the body. Thus net force will be zero.
Conclusion:
Thus, the net force on a heavy trunk when it is at rest on the floor is zero.
(b)
The net force on a heavy trunk when it is being slid across the floor at constant speed.
Answer to Problem 1FTD
The net force on a heavy trunk when it is being slid across the floor at constant speed is zero.
Explanation of Solution
According to Newton’s first law of motion a body will remain in uniform motion until it is acted upon by external unbalanced force. Therefore the net force acting on a body in uniform motion is zero.
The forces acting on the trunk are the weight of the trunk which is acting downward and normal reaction which is acting upward, driving force along the direction of motion, air resistance opposite to the direction of force and friction opposite to the direction of motion. The normal reaction balances weight of the trunk and driving force balances the sum of air resistance and friction. Thus net force acting on a constant speed car is zero.
Conclusion:
Thus, the net force on a heavy trunk when it is being slid across the floor at constant speed is zero.
(c)
The net force on a heavy trunk when it is being pulled upward in an elevator whose cable tension equals the combined weight of the elevator and trunk.
Answer to Problem 1FTD
The net force on a heavy trunk when it is being pulled upward in an elevator whose cable tension equals the combined weight of the elevator and trunk is zero.
Explanation of Solution
According to Newton’s first law of motion a body will remain in uniform motion until it is acted upon by external unbalanced force.
The forces acting on the elevator and trunk is the weight of the body acting downward and tension of the cable acting upward. Since both are same net force acting on the system is zero. Thus total acceleration is zero. Therefore net force on elevator and trunk is zero.
Conclusion:
Thus, the net force on a heavy trunk when it is being pulled upward in an elevator whose cable tension equals the combined weight of the elevator and trunk is zero
(d)
The net force on a heavy trunk when it is sliding down a frictionless ramp.
Answer to Problem 1FTD
The net force on a heavy trunk when it is sliding down a frictionless ramp is parallel to the ramp.
Explanation of Solution
According to Newton’s first law of motion a body will move with acceleration only if there is any net force acting on it.
Normal force balances the perpendicular component of the weight. Therefore, body slides along the slope as a result of parallel component of the weight.
Conclusion:
Thus,the net force on a heavy trunk when it is sliding down a frictionless ramp is parallel to the ramp.
Want to see more full solutions like this?
Chapter 5 Solutions
Essential University Physics (3rd Edition)
Additional Science Textbook Solutions
Laboratory Experiments in Microbiology (12th Edition) (What's New in Microbiology)
Campbell Biology (11th Edition)
Anatomy & Physiology (6th Edition)
Human Biology: Concepts and Current Issues (8th Edition)
Biology: Life on Earth with Physiology (11th Edition)
Applications and Investigations in Earth Science (9th Edition)
- A car is stuck in the mud. A tow truck pulls on the car with the arrangement shown in Fig. P4.32. The tow cable is under a tension of 2 500 N and pulls downward and to the left on the pin at its upper end. The light pin is held in equilibrium by forces exerted by the two bars A and B. Each bar is a strut; that is, each is a bar whose weight is small compared to the forces it exerts and which exerts forces only through hinge pins at its ends. Each strut exerts a force directed parallel to its length. Determine the force of tension or compression in each strut. Proceed as follows. Make a guess as to which way (pushing or pulling) each force acts on the top pin. Draw a free-body diagram of the pin. Use the condition for equilibrium of the pin to translate the free-body diagram into equations. From the equations calculate the forces exerted by struts A and B. If you obtain a positive answer, you correctly guessed the direction of the force. A negative answer means that the direction should be reversed, but the absolute value correctly gives the magnitude of the force. If a strut pulls on a pin, it is in tension. If it pushes, the strut is in compression. Identify whether each strut is in tension or in compression.arrow_forwardDoes the ground need to exert a force on you for you to jump off the ground, or do you need to exert a force on the ground? If the ground must exert a force on you, is that force greater than the force you exert on the ground?arrow_forwardA large crate of mass m is placed on the flatbed of a truck but not tied down. As the truck accelerates forward with acceleration a, the crate remains at rest relative to the truck. What force causes the crate to accelerate? (a) the normal force (b) the gravitational force (c) the friction force (d) the ma force exerted by the crate (e) No force is required.arrow_forward
- A black widow spider hangs motionless from a web that extends vertically from the ceiling above. If the spider has a mass of 1.5 g, what is the tension in the web?arrow_forwardCalculate the force required to pull a stuffed toy duck (mass m = 1.25 kg) at a constant velocity of 3.6 m/s horizontally across the floor if the string is 50.0 above the horizontal. The coefficient of kinetic friction between the duck and the floor is 0.70.arrow_forwardBy what factor does the drag force on a car increase as it goes from 65 to 110 km/h?arrow_forward
- The manager of a department store is pushing horizontally with a force of magnitude 200 N on a box of shirts. The box is sliding across the horizontal floor with a forward acceleration. Nothing else touches the box. What must be true about the magnitude of the force of kinetic friction acting on the box (choose one)? (a) It is greater than 200 N. (b) It is less than 200 N. (c) It is equal to 200 N. (d) None of those statements is necessarily true.arrow_forwardConsider a sky surfer falling through air, as in Figure 5.18, before reaching his terminal speed. As the speed of the sky surfer increases, the magnitude of his acceleration (a) remains constant, (b) decreases until it reaches a constant nonzero value, or (c) decreases until it reaches zero.arrow_forwardYou are playing with your daughter in the snow. She sits on a sled and asks you to slide her across a flat, horizontal field. You have a choice of (a) pushing her from behind, by applying a force downward on her shoulders at 30 below the horizontal (Fig. 5.2a) or (b) attaching a rope to the front of the sled and pulling with a force at 30 above the horizontal (Fig 5.2b). Which would be easier for you and why?arrow_forward
- A crate with a mass of 155 kg, starting from rest, slides down a ramp making an angle of 32 degrees with respect to horizontal. The ramp is 3 meters long. A constant frictional force of 100 N acts throughout the motion and a force F is being applied by a rope as shown to prevent the block from sliding too fast.arrow_forwardI need solution :))arrow_forwardA couple consists of two forces which have different magnitudes and parallel noncollinear lines of action but which are opposite in sense. O False O Truearrow_forward
Glencoe Physics: Principles and Problems, Student...PhysicsISBN:9780078807213Author:Paul W. ZitzewitzPublisher:Glencoe/McGraw-Hill
Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning
College PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning
College PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning
University Physics Volume 1PhysicsISBN:9781938168277Author:William Moebs, Samuel J. Ling, Jeff SannyPublisher:OpenStax - Rice University