Work-Energy Theorem: Homework Statement & Solution

AI Thread Summary
The discussion focuses on a homework problem involving a mass in circular motion on a frictionless table, where the radius changes as the string is pulled. The key task is to demonstrate that the work done in pulling the string corresponds to the increase in the mass's kinetic energy. Participants suggest using conservation of angular momentum and the definition of work done by the tension in the string, along with integration techniques, to solve the problem. There is a mention of path independence of work done by a central force, indicating a potential approach to the solution. Overall, the conversation emphasizes applying fundamental physics principles to derive the relationship between work and kinetic energy in this scenario.
jgens
Gold Member
Messages
1,575
Reaction score
50

Homework Statement



A mass m whirls on a frictionless table, held to circular motion by a string which passes though a hole in the table. The string is slowly pulled through the hole so that the radius of the circle changes from l1 to l2. Show that the work done in pulling the string equals the increase in kinetic energy of the mass.

Homework Equations



N/A

The Attempt at a Solution



I've already shown that the work done by a central force is path independent. Can I just apply the same manipulations used to get the work energy theorem in cartesian coordinates? I'm really not sure so I could use some guidance here.
 
Physics news on Phys.org
hi jgens! :wink:

i'll guess that they want you to use conservation of angular momentum , the definition of the work done (by the tension in the string), and a bit of integration :smile:
 

Thread 'Rolling without slipping on a curved surface'

Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
View full post »
Thread 'Voltmeter readings for this circuit with switches'

Thread 'Voltmeter readings for this circuit with switches'

TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
View full post »

Similar threads

Work energy KE theorem for a book being lifted up in a gravitional field
Replies
18
Views
2K
Misunderstanding Work-energy theorem and center of mass properties
Replies
7
Views
2K
Work and Energy on a Slope - How Does a Block Move Up with Zero Net Work?
Replies
3
Views
2K
Solving a Motion Problem with Work-Energy Theorem
Replies
23
Views
2K
Understanding Work-Energy Theorem: Solving an Exercise with Different Solutions
Replies
11
Views
3K
Constant rotational kinetic energy
Replies
1
Views
1K
Energy analysis of a particle moving in a shrinking circle
Replies
17
Views
4K
Understanding the Work-Energy Theorem: Solving the Roller Coaster Problem
Replies
8
Views
3K
Capacitor+work energy theorem problem
Replies
18
Views
2K
Is this work-energy theorem for a system correct?
Replies
12
Views
3K

Hot Threads

Recent Insights

Back
Top