Finding forces acting on spring/pulley system

  • Thread starter uglies1992
  • Start date
  • #1

Homework Statement



There is a spring attached to a hanging block by a rope over a pulley, with a stop on the other end. Using basic physic principles, determine the relationship between spring extension and weight of the block.

Homework Equations


F=-kd
w=mg

The Attempt at a Solution


I know that if the system is in equilibrium, the sum of forces acting on the block/spring should be zero. Also, since the force of the rope on the block and the force of the rope on the spring are third law pairs, they should be equal in magnitude but in opposite directions. Not quite sure where to go from here though.
 

Answers and Replies

  • #2
785
15

Homework Statement



There is a spring attached to a hanging block by a rope over a pulley, with a stop on the other end. Using basic physic principles, determine the relationship between spring extension and weight of the block.

Homework Equations


F=-kd
w=mg

The Attempt at a Solution


I know that if the system is in equilibrium, the sum of forces acting on the block/spring should be zero. Also, since the force of the rope on the block and the force of the rope on the spring are third law pairs, they should be equal in magnitude but in opposite directions. Not quite sure where to go from here though.

Not like this.

Hint: First consider the axle of the pulley as the system and not the whole pulley. Consider equilibrium of spring and axle of pulley. What equation can you make for this ?
 
  • #3
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
11,389
1,044

Homework Statement



There is a spring attached to a hanging block by a rope over a pulley, with a stop on the other end. Using basic physic principles, determine the relationship between spring extension and weight of the block.

Homework Equations


F=-kd
w=mg

The Attempt at a Solution


I know that if the system is in equilibrium, the sum of forces acting on the block/spring should be zero. Also, since the force of the rope on the block and the force of the rope on the spring are third law pairs, they should be equal in magnitude but in opposite directions. Not quite sure where to go from here though.
Hello uglies1992 . Welcome to PF !

The force of the rope on the block and the force of the rope on the spring are not a third law pair .

The force of the rope on the block and the force of the block on the rope is a third law pair .

Similarly, the force of the spring on the block and the force of the spring on the rope is a third law pair .

There are also the force of the rope on the pulley and the force of the pulley on the rope to consider.
 
Last edited:

Related Threads on Finding forces acting on spring/pulley system

Replies
6
Views
14K
Replies
6
Views
2K
  • Last Post
Replies
15
Views
1K
Replies
31
Views
4K
  • Last Post
Replies
4
Views
4K
  • Last Post
Replies
9
Views
6K
  • Last Post
Replies
3
Views
10K
Replies
1
Views
1K
Replies
3
Views
1K
Replies
18
Views
13K
Top