Uniform circular motion - origin of speed

  • #1

Main Question or Discussion Point

I am having trouble understanding tangential speed as it applies to uniform circular motion and I would appreciate any help.

Say I have a ball on the end of a string that I hold with my hand and rotate at a constant speed. If the string provides the centripetal force and acceleration, where does the speed come from? what provides it?
 
Last edited by a moderator:

Answers and Replies

  • #2
TSny
Homework Helper
Gold Member
12,315
2,804
Notice what your hand is doing while you are bringing the ball from rest up to its final speed.
 
  • #3
As I am bringing it to its final speed, my hand is moving in arc. So my hand is also providing the speed?
 
  • #4
TSny
Homework Helper
Gold Member
12,315
2,804
As I am bringing it to its final speed, my hand is moving in arc. So my hand is also providing the speed?
Yes. As the ball is first brought into motion, the string is not perpendicular to the velocity.

Look at this video at about time 45 seconds.


Here is a snapshot soon after the ball is first set into motion.
upload_2018-1-16_12-31-12.png

You can see that the string is not perpendicular to the velocity.
 

Attachments

  • #5
Awesome. Thanks a lot, your vector pic. really helped.
 

Related Threads for: Uniform circular motion - origin of speed

  • Last Post
Replies
10
Views
2K
  • Last Post
Replies
2
Views
10K
  • Last Post
2
Replies
38
Views
3K
  • Last Post
Replies
2
Views
2K
  • Last Post
2
Replies
33
Views
4K
  • Last Post
Replies
11
Views
2K
Replies
5
Views
678
  • Last Post
Replies
3
Views
3K
Top