Tension in a string simple pendulum

  • Thread starter aurao2003
  • Start date
  • #1
126
0

Homework Statement




Hi Guys
I obtained a slighty different answer. Can anyone kindly verify where I am going wrong? The question is stated thus:
A simple pendulum is of length 0.5m and the bob has mass 0.25kg. Find the greatest value for the tension in the string when the pendulum is set in oscillation by drawing the bob to one side through an angle of 5 degrees and releasing from rest. Explain where in the cycle the tension is greatest.

Te relationship for centripetal force involved is
T-mg = mv^2/r
Resolving the tension in the string into its components,
Tcos theta = mg
Tsin theta =mv^2/r
Dividing the above, we obtain
tan theta =v^2/gr
So, v^2 = gr tan theta
I substituted this value and other values for mass and g. I obtained 2.7N as my final answer. But it appears to be 2.5N. Any clarification will be appreciated. Thanks.

Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
294
0
Te relationship for centripetal force involved is
T-mg = mv^2/r
Resolving the tension in the string into its components,
Tcos theta = mg
Tsin theta =mv^2/r
Dividing the above, we obtain
tan theta =v^2/gr
So, v^2 = gr tan theta
I substituted this value and other values for mass and g. I obtained 2.7N as my final answer. But it appears to be 2.5N. Any clarification will be appreciated. Thanks.
When you say Tsin theta =mv^2/r, do you mean to imply that the horizontal component of tension is the centripital force?
 
  • #3
126
0
When you say Tsin theta =mv^2/r, do you mean to imply that the horizontal component of tension is the centripital force?
Yes. That is my assumption. I have a feeling it may not be valid. Is tension equal to the weight at the point of rest?
 
  • #4
1,065
10
Your are calculating the tension T at its highest position.
Maximum tension is at its lowest position.
At this position, the PE at the top is converted to maximum kinetic energy.
Find this velocity from conservation of energy.
 

Related Threads on Tension in a string simple pendulum

Replies
4
Views
2K
  • Last Post
Replies
2
Views
5K
  • Last Post
Replies
3
Views
4K
Replies
1
Views
10K
  • Last Post
Replies
11
Views
4K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
6
Views
5K
  • Last Post
Replies
1
Views
4K
Replies
3
Views
2K
Replies
4
Views
13K
Top