Period of a rotating mass held by two strings

AI Thread Summary
The discussion revolves around a physics problem involving a 4.00 kg block attached to a vertical rod by two strings, focusing on the tension in the strings and the system's rotational speed. The tension in the upper string is given as 82.0 N, and the participant is attempting to calculate the tension in the lower string using the y-component of forces. They express confusion about the appropriate formulas to use for calculating the system's revolutions per minute and how to determine when the lower cord goes slack. The conversation emphasizes the need to apply the correct equations related to force and circular motion to solve the problem effectively. The participants are seeking clarity on the equations and their applications in this context.
limekiwi
Messages
2
Reaction score
0

Homework Statement



The 4.00kg block in the figure (Intro 1 figure) is attached to a vertical rod by means of two strings. When the system rotates about the axis of the rod, the strings are extended as shown in the diagram and the tension in the upper string is 82.0 N.

intro1image.jpg


Homework Equations



a) What is the tension in the lower cord?
b) How many revolutions per minute does the system make?
c) Find the number of revolutions per minute at which the lower cord just goes slack.

The Attempt at a Solution



a) I need to focus on the y-component so..
T1 cos\theta - T2 cos\theta - mg = 0
I find \theta by taking the triangle formed by the rod and two strings...
image2.jpg

cos\theta = 1/1.25
With all this info.. I can find T2. Correct?

b) I know the formula for T is T = (2\pir) / V... or T = 2\pi*[(Lcos\theta)/g]^1/2
Do I actually use this formula? I am a bit confused since later I have to find T when the lower cord slacks. Can someone clear this up for me? :smile:
 
Physics news on Phys.org
limekiwi said:
a) ... With all this info.. I can find T2. Correct?

Yes, correct.

b) I know the formula for T is T = (2\pir) / V... or T = 2\pi*[(Lcos\theta)/g]^1/2
Do I actually use this formula? I am a bit confused since later I have to find T when the lower cord slacks. Can someone clear this up for me? :smile:

What equation involves force and circular motion?
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Two masses on a rotating platform
Replies
3
Views
2K
Looking for observed rotation periods of various Foucault pendulums at different latitudes
Replies
6
Views
809
Releasing a rod tied to a string which was held at an angle
Replies
3
Views
1K
Find the tension in the lower string and the rotation rate
Replies
9
Views
4K
Rope between inclines with maximum length of hanging middle portion
Replies
46
Views
2K
To find the modulus of elasticity of a light elastic string
Replies
7
Views
2K
What is the maximum tension and friction force for a block held on an incline?
Replies
19
Views
4K
Angle that makes kinetic and potential energy of simple pendulum equal
Replies
2
Views
1K
Tension Force between two rotating masses on strings
Replies
1
Views
3K
How can I find the velocity of a point on a disk rotating in a disc?
Replies
16
Views
2K

Hot Threads

Recent Insights

Back
Top