Finding Acceleration and Tension, With Friction

Click For Summary
SUMMARY

The discussion centers on solving a physics problem involving two blocks and a ball, with a coefficient of kinetic friction of 0.30. The user attempts to calculate the tensions (T1 and T2) and the acceleration of the blocks using free-body diagrams and Newton's second law. The user arrives at a tension value of T1 as 20.906N, while the correct answer is 17N. A critical error identified in the calculations is a miscalculation of a constant, where the final number should be 8.82 instead of 88.2.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with free-body diagrams
  • Knowledge of frictional forces and coefficients
  • Basic algebra for solving equations
NEXT STEPS
  • Review the principles of free-body diagrams in physics
  • Study the effects of friction on motion in mechanics
  • Learn how to apply Newton's second law to multi-body systems
  • Practice solving tension problems in pulley systems
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators looking for examples of tension and friction problems in multi-body systems.

VACA
Messages
16
Reaction score
0

Homework Statement


In figure P4.52 (below), the coefficient of kinetic friction between two blocks shown is 0.30. The surface of the table and the pulleys are frictionless. (a) Draw a free-body diagram for each block. (b) Determine the acceleration of each block. (c) Find the tension in the strings.

p4_56.gif



Homework Equations


Since all accelerations are equal:
-a2 = a3 = -a10

Also, a = F/m
And for gravity: Fg=m (in kg)*9.8


The Attempt at a Solution



For the force diagram I know that the 2kg block will have T1 pulling it to the left and friction pulling it to the right. The 3kg block will have T2 pulling it to the right and friction and T1 pulling to the left. And the 10kg ball, sphere, whatever, has T2 pulling upward and gravity pulling downward.

Fk is 5.88N since Fn is 19.6N (0.3*19.6).
And Fg is 98N.

- (5.88N - T1) / 2kg = (T2 - T1 - 5.88N) / 3kg = - (T2 - 98N) / 10kg Got rid of my fractions, LCD of 30...

15T1 - 88.2N = 10T2 - 10T1 -58.8N = 294N - 3T2 Used the first two equations to solve for T2

2.5T1 - 2.94N = T2 Plugged into the last 2 equations and ended up getting...

25T1 - 29.4N - 10T1 - 58.8N = 294N - 7.5T1 + 88.2N

T1 = 20.906N


The correct answer for T1 is 17N. I've looked over my work and couldn't find a mistake in my math, though I'm sure there is. I need help figuring out where I messed up.

I hope this isn't just some dumb mistake because I've spent so long on this single problem.

Thanks in advance.
 
Physics news on Phys.org
VACA said:
25T1 - 29.4N - 10T1 - 58.8N = 294N - 7.5T1 + 88.2N


All is Ok except for a small mistake. Last number is not 88.2 but 8.82.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
6
Views
2K
  • · Replies 3 ·
Replies
3
Views
5K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 64 ·
3
Replies
64
Views
14K
Replies
7
Views
4K
Replies
30
Views
4K