• Support PF! Buy your school textbooks, materials and every day products Here!

Principle of Conversation Of Energy question

  • #1

Homework Statement



2 objects are connected by a light string passing over a light frictionless pulley. The 5kg object is released from rest. Using the principle of conservation of energy, (a) determine the speed of the 3kg object just as the 5kg object hits the ground


The picture shows the 3kg object at rest connected by a string to a pulley vertically....and the 5kg object hangin from a string from the pulley with 4m height between the ground and the 5kg object.




Homework Equations



4.43m/s is answer to a



The Attempt at a Solution



.5mv^2 + g(mf-mi)y=.5(5)v^2 + (-9.8)(2)(4)===>

2.5v^2= 78.4
v=5.6m/s
 
Last edited:

Answers and Replies

  • #2
rl.bhat
Homework Helper
4,433
5
When the 5kg object is released from rest, its acceleration in not g. Calculate its acceleration by drawing free body diagram. 3 kg moves up with the same acceleration. Then apply the conservation of energy for 3 kg mass to calculate its velocity.
 
  • #3
335
0
Draw An F.b.d.
 

Related Threads for: Principle of Conversation Of Energy question

  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
5
Views
875
  • Last Post
Replies
1
Views
4K
  • Last Post
Replies
4
Views
172
Replies
10
Views
1K
Replies
7
Views
7K
  • Last Post
Replies
3
Views
898
  • Last Post
Replies
1
Views
1K
Top