Giancoli 7th Edition textbook cover
Giancoli's Physics: Principles with Applications, 7th Edition
4
Dynamics: Newton's Laws of Motion
Change chapter

4-4 to 4-6: Newton's Laws, Gravitational Force, Normal Force
4-7: Newton's Laws and Vectors
4-8: Newton's Laws with Friction, Inclines

Question by Giancoli, Douglas C., Physics: Principles with Applications, 7th Ed., ©2014, Reprinted by permission of Pearson Education Inc., New York.
Problem 20
Q

A box weighing 77.0 N rests on a table. A rope tied to the box runs vertically upward over a pulley and a weight is hung from the other end (Fig. 4–45). Determine the force that the table exerts on the box if the weight hanging on the other side of the pulley weighs

  1. 30.0 N,
  2. 60.0 N, and
  3. 90.0 N.
Problem 20.
Figure 4-45.
A
  1. 47.0 N47.0\textrm{ N}
  2. 17.0 N17.0\textrm{ N}
  3. 00
Giancoli 7th Edition, Chapter 4, Problem 20 solution video poster
Padlock

In order to watch this solution you need to have a subscription.

VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. Here's a free body diagram of the box that's on the table, there's a force exerted upwards and due to the hanging weight on the other side of the pulley, and this force up is due to the weight will be equal to the weight of the weight. And there's also going to be a normal force upwards on this box due to the table. And the box has a gravity force downwards of 77.0 Newtons. So, the net force on this box is zero because it's not accelerating and that means the up forces equal the down forces. So, the up force total is the normal force plus the force of the weight that's hanging, and that equals the down force total which is just gravity. And we can solve for the normal force by subtracting force of the weight from both sides. So, the normal force is Fg minus Fw. So, in part A that's 77 Newtons minus the 30 Newtons of the hanging weight which is 47 Newtons upwards. And then in Part B it's 77 minus 16 Newtons, so, that's that 17 Newtons normal force. And then in Part C there's no normal force since the hanging weight has a weight of 90 Newtons which is greater than the weight of this box and so the box won't even be touching the floor and so the floor will not be exerting any normal force at all because this box is going to accelerate upwards.

Find us on:

Facebook iconTrustpilot icon
Giancoli Answers, including solutions and videos, is copyright © 2009-2024 Shaun Dychko, Vancouver, BC, Canada. Giancoli Answers is not affiliated with the textbook publisher. Book covers, titles, and author names appear for reference purposes only and are the property of their respective owners. Giancoli Answers is your best source for the 7th and 6th edition Giancoli physics solutions.