Is This Free Body Diagram of a Pendulum Correct?

In summary, the homework statement asks for a free body diagram of a pendulum and a bob with a maximum amplitude of 30 degrees. The attempt at a solution attached has the correct angle and period.
  • #1
-EquinoX-
564
1

Homework Statement


I am asked to draw a free body diagram of a pendulum and a bob with it's maximum
amplitude of 30 degrees. Below is my attempt, I just forgot to say that theta is equal to
30 degrees, other than that is it right?

Homework Equations


none

The Attempt at a Solution


attached as a picture

http://img246.imageshack.us/img246/7276/pendulumqa2.jpg
 
Last edited by a moderator:
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  • #2
Looks good to me.
 
  • #3
reason I am not so sure is because of the amplitude of 30 degrees, what does that mean?
 
  • #4
The amplitude is just a measure of how far the pendulum bob swings away from equilibrium (the vertical). An amplitude of 30 degrees means that the pendulum swings until it's 30 degrees from the vertical before swinging back.

You've reflected the angle in your diagram, so you're OK.
 
  • #5
ok, and the period of this pendulum is basically the time it takes the position I move the pendulum 30 degrees away from the equilibrium then I release it and it goes back again to the same position right?
 
  • #6
I think your theta should be flipped to the bottom. Currently, your amplitude is 150[tex]^{o}[/tex].
 
Last edited:
  • #7
-EquinoX- said:
ok, and the period of this pendulum is basically the time it takes the position I move the pendulum 30 degrees away from the equilibrium then I release it and it goes back again to the same position right?
Right. The period is the time it takes for one complete cycle. If it starts out to the right at 30 degrees at t=0, then in one period it will have gone to equilibrium, moved to the left at 30 degrees, come back to equilibrium and then back to the starting point at 30 degrees to the right.
 
  • #8
kevtimc said:
I think your theta should be flipped to the bottom. Currently, your amplitude is 150[tex]^{o}[/tex].
No, the angle shown is the correct amplitude.
 
  • #9
Doc Al said:
Right. The period is the time it takes for one complete cycle. If it starts out to the right at 30 degrees at t=0, then in one period it will have gone to equilibrium, moved to the left at 30 degrees, come back to equilibrium and then back to the starting point at 30 degrees to the right.

ok, thanks that helped a lot... so in one period it passes the equilibrium point twice then
 
  • #10
Doc Al said:
No, the angle shown is the correct amplitude.

EDIT: Nevermind, I see the image now, and I missed the T part. It's correct.
 

Related to Is This Free Body Diagram of a Pendulum Correct?

1. What is a free body diagram?

A free body diagram is a visual representation of all the forces acting on an object. It shows the direction and magnitude of each force, and is used to analyze the motion of the object.

2. How is a free body diagram of a pendulum different from other objects?

A free body diagram of a pendulum is unique because it includes the force of gravity acting on the mass of the pendulum, as well as the tension force from the string or rod that the pendulum is attached to.

3. What are the key components of a free body diagram of a pendulum?

The key components of a free body diagram of a pendulum include the pendulum mass, the string or rod it is attached to, the force of gravity acting on the mass, and the tension force from the string or rod.

4. How can a free body diagram of a pendulum be used to analyze its motion?

By using the free body diagram, we can determine the net force acting on the pendulum and its direction. This information can be used to calculate the acceleration of the pendulum and predict its motion.

5. Are there any assumptions or limitations when using a free body diagram of a pendulum?

One key assumption is that the pendulum is in a uniform gravitational field. This means that the force of gravity is constant and acts in the same direction at all points along the pendulum's swing. Other limitations may include ignoring air resistance and assuming the string or rod is massless and does not stretch or bend.

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