Conservation of Energy and frictionless pulley?

AI Thread Summary
The discussion revolves around a physics problem involving a 20.0 kg block and a 30.0 kg block connected by a string over a frictionless pulley, with the latter connected to a spring. The blocks are released from a specific position, and the goal is to determine their speed when the 30.0 kg block is 20.0 cm above the floor. Participants emphasize the importance of applying the conservation of energy principle, specifically the equation relating kinetic and potential energy. There is a request for clarification on the arithmetic calculations leading to a proposed answer of 1.1687 m/s^2. The need for a visual reference of the setup is also highlighted to better understand the problem dynamics.
Eukanuba863
Messages
4
Reaction score
0

Homework Statement


A 20.0 kg block is connected to a 30.0 kg block by a string that passes over a light, frictionless pulley. The 30.0 kg block is connected to a spring that has negligible mass and a force constant of 240 N/m, as shown in the figure below. The spring is unstretched when the system is as shown in the figure, and the incline is frictionless. The 20.0 kg block is pulled 18.0 cm down the incline (so that the 30.0 kg block is 38.0 cm above the floor) and released from rest. Find the speed of each block when the 30.0 kg block is 20.0 cm above the floor (that is, when the spring is unstretched).



Homework Equations



(K-U)sub(i)=(K-U)sub(f)

The Attempt at a Solution



i've talked with multiple physics teachers on this problem every body got different anwsers...

i'm almost convinced the anwser is 1.1687 m/s^2

Could you help me please?
 
Physics news on Phys.org
I need to see the figure. I can't tell the angle of the incline, wether there is one or 2 springs, and in what direction they pull etc.
 
here is the image...

A 20.0 kg block is connected to a 30.0 kg block by a string that passes over a light, frictionless pulley. The 30.0 kg block is connected to a spring that has negligible mass and a force constant of 240 N/m, as shown in the figure below. The spring is unstretched when the system is as shown in the figure, and the incline is frictionless. The 20.0 kg block is pulled 18.0 cm down the incline (so that the 30.0 kg block is 38.0 cm above the floor) and released from rest. Find the speed of each block when the 30.0 kg block is 20.0 cm above the floor (that is, when the spring is unstretched).

p7-45.gif
 
Eukanuba863 said:

Homework Equations



(K-U)sub(i)=(K-U)sub(f)
You want conservation of energy--that's not quite it. Mechanical energy equals KE + PE. (You have multiple forms of PE to track in this problem.)
i'm almost convinced the anwser is 1.1687 m/s^2
Show how you got that.
 
i know the parts just will you check my aritmatic?

it's

(K+U)initial=(K+U)final

and i know all the spring constant parts with .5kx^2, mgh etc.
 
please

could you just check my arithmetic please?
 
Show us your arithmetic so we can check it.
 

Similar threads

Spring potential Problem Reference Point
Replies
14
Views
3K
Understanding why the initial height of one block is equal t
Replies
33
Views
3K
Two blocks connected with spring and pulley
Replies
1
Views
4K
Distribution of Energy when work is done on a system of 2 masses connected by a spring
Replies
17
Views
1K
Potential energy incline problem
Replies
2
Views
2K
Time period of SHM & Energy conservation in pulley-spring-block system
Replies
24
Views
3K
A system comprising blocks, a light frictionless pulley, and
Replies
6
Views
4K
Finding the Coefficient of Friction in a Spring-Block Incline System
Replies
2
Views
2K
Spring and block on an inclined plane
Replies
27
Views
9K
Two blocks on a plane with a pulley
Replies
11
Views
2K

Hot Threads

Recent Insights

Back
Top