Masses connected to spring momentum

AI Thread Summary
In the discussion, a problem involving two blocks connected by a spring on a frictionless table is analyzed. The first scenario has one block stationary while the other moves after the spring is released, achieving a speed of 2.0 m/s. In the second scenario, both blocks are released simultaneously, and the user attempts to calculate the speed of the lighter block using conservation of momentum principles. The user arrives at a speed of 1.79 m/s for the lighter block, but this is identified as incorrect, prompting a request for clarification on the formulas used and their applicability to the scenario. The conversation highlights the importance of correctly applying conservation laws in spring-mass systems.
Raj Kishore
Messages
6
Reaction score
0
Homework Statement
An m = 1.3 kg block and an M = 3.0 kg block have a spring compressed between them and rest on a frictionless table. With a stopper in place that prevents m from moving, the spring is compressed and released so that M moves away with a speed 2.0 m/s.

q17 com.png


The spring is compressed exactly as before, but this time without the stopper in place. Both blocks are released at the same time. What is the speed of mass m when the spring stops acting on it?

The attempt at a solution
What I did to solve this was I used the equation vfM = 2vCM - v0M

vCM = (Mv0M + mv0m)/(m+M)

Then I said Mv0M = mvfm + MvfM

So, (Mv0M - MvfM)/m = vfm

I got the final answer to be 1.79 m/s, but it is wrong. Thanks for helping.
 
Physics news on Phys.org
Can you explain your reasoning a bit more? Where did vfM = 2vCM - v0M come from, for example?
 
That is a formula we were taught
 
Well, it seems wrong to me. How do you know is applies here?
 
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »

Similar threads

Distribution of Energy when work is done on a system of 2 masses connected by a spring
Replies
17
Views
1K
Question about springs and rotational/translational energy
Replies
4
Views
1K
How High Does Cheese Rise on a Released Spring?
Replies
1
Views
1K
A block of mass m is dropped onto the top of a vertical spring....
Replies
8
Views
5K
Question about momentum and kinetic energy.
Replies
5
Views
2K
Mech#3 on 1974 AP "C" Exam -- 2 Blocks Connected by a Spring
Replies
3
Views
2K
Compression of a spring by an object in free fall
Replies
8
Views
3K
Conservation of momentum in a bullet-block-spring system
Replies
6
Views
2K
AP Physics C Momentum Problem: A dart launched horizonally by a spring gun
Replies
22
Views
4K
Final velocity of two blocks between a spring
Replies
2
Views
3K

Hot Threads

Recent Insights

Back
Top