Concept explainers
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
Modified Mastering Physics With Pearson Etext -- Standalone Access Card -- For Essential University Physics (3rd Edition)
Additional Science Textbook Solutions
Physics: Principles with Applications
Tutorials in Introductory Physics
Introduction to Electrodynamics
An Introduction to Thermal Physics
University Physics with Modern Physics (14th Edition)
- Check Your Understanding One end of a 3.0-m rope is tied to a tree; the other, end is tied to a car stuck in the mud. The motorist pulls sideways on the midpoint of the rope, displacing it a distance of 0.25 m. If he exerts a force of 200.0 N under these conditions, determine the force exerted on the car.arrow_forwardWhat is the condition for motion when more than one force acts?arrow_forwardFind the acceleration of the body of mass 5.0 kg shown below.arrow_forward
- Two masses are attached to a spring scale as shown in Fig. 3.25. If both masses are 1 kg, which force, in newtons, would the scale read? (Hint: Think of holding a free end of the rope on one side of the scale with only the weight on the other.) Figure 3.25 What Does the Scale Read? See Short Answer 16.arrow_forwardShow that the acceleration of any object down a frictionless incline that makes an angle with the horizontal is a=gsin . (Note that this acceleration is independent of mass.)arrow_forwardBy what factor does the drag force on a car increase as it goes from 65 to 110 km/h?arrow_forward
- The two barges shown here are coupled by a cable of negligible mass. The mass of the front barge is 2.00103kgand the mass of the rear barge is 3.00103kg . A tugboat pulls the front barge with a horizontal force of magnitude 20.0103N . and the frictional forces of the water on the front and rear barges are 8.00103Nand 10.0103N . respectively. Find the horizontal acceleration of the barges and the tension in the connecting cable.arrow_forwardIn the absence of air resistance, which will fall first to the ground..... a handkerchief or a metal hammer? Why?arrow_forwardA safe weighing 10 tons is to be loaded on a truck 5 ft high by means of planks 20 ft long. If it requires 350 lbto overcome friction on the skids, find the least force necessaryto move the safe.arrow_forward
- the two boxes have identical masses of 40 kg. Both experience a sliding friction force with u 0.15. Find the acceleration of the boxes and the tension in the tie cord.arrow_forwardA certain cable of an elevator is designed to exert a force of 4.5 × 10^4 N. If the maximum acceleration that a loaded car can withstand is 3.5 m/s2, what is the combined mass of the car and its contents?arrow_forwardA freight train has a mass of 1.5 x 107 kg. If the locomotivecan exert a constant pull of 7.5 x 105 N, how long does it taketo increase the speed of the train from rest to 80 km/h?arrow_forward
- University Physics Volume 1PhysicsISBN:9781938168277Author:William Moebs, Samuel J. Ling, Jeff SannyPublisher:OpenStax - Rice UniversityPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningAn Introduction to Physical SciencePhysicsISBN:9781305079137Author:James Shipman, Jerry D. Wilson, Charles A. Higgins, Omar TorresPublisher:Cengage Learning