Force Systems Multiple Choice Thread

Click For Summary
The discussion revolves around a physics problem involving two blocks connected by a string over a pulley, with a known acceleration of 0.6g. The key challenge is to determine the mass ratio M2/M1. A user successfully calculated the tension in the string as 0.4 M2 * g and confirmed their acceleration value. They received guidance to substitute the tension into their free body analysis for M1, which ultimately led to solving the problem. The conversation highlights the importance of applying force equations and free body diagrams in solving dynamics problems.
RoboNerd
Messages
410
Reaction score
11

Homework Statement



http://gpschools.schoolwires.net/cms/lib05/MI01000971/Centricity/Domain/272/Chapter%205%20MC%2013.pdf
It is problem 22 on page 7 of the document:

A block of mass M1 on a horizontal table is connected to a hanging block of mass M2 by a string that passes over a pulley, as shown. The acceleration of the blocks is 0.6g. Assume that the friction and the mass of the string are negligible.
upload_2016-3-19_18-31-27.png


22. The ratio of masses M2 / M1 is
(A)0.67
(B) 1.0
(C) 1.4
(D)1.5
(E) 1.6

[Note: Post edited by moderator to include the problem statement content in-post]

Homework Equations



F=ma

The Attempt at a Solution


[/B]
OK. I know that this is a force system, and I would draw the free body diagrams for each and write out the equations for each block and solve. So I was able to get the tension T in the string to be 0.4 M2 * g. I was also able to get a=0.6 g. My numbers so far are correct.

However, I am at a loss for finding the ratio of masses M2/M1. Could anyone help me, please? Thanks?
 
Last edited by a moderator:
Physics news on Phys.org
Since you have found the tension as a function of M2, substitute that value for T in your equation that you determined from your free body analysis of M1.
 
Thanks for that hint! I solved it!
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

  • · Replies 5 ·
Replies
5
Views
1K
Replies
6
Views
1K
Replies
8
Views
10K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 8 ·
Replies
8
Views
11K
  • · Replies 2 ·
Replies
2
Views
2K