# Homework Help: Calculating Normal force when object it in circular motion.

1. Nov 5, 2007

### Kingrick

\ P ____T_______
\ / \
\ / \
\ / \
\ / \
\ | R |
\ | | |- Q
\ | | |
\ \ | /
\ \ | /
\ \ | /
_____\______|______/

try and picture this more circle like.

1. The problem statement, all variables and given/known data

A small block with mass m=0.100kg can slide along the frictionless loop-the-loop, with loop radius R=0.15m, an initial velocity along the track of vi= 2.0 m/s at point P, at height h=2.0R above the bottom loop.

ok now, so first part to the question is,

determine the normal force that the track exerts on the block when it is at the point Q. Include a FBD in your answer and cleraly identify the laws of physics that are used to solve the problem.

2. Relevant equations
f=ma
PE=KE

3. The attempt at a solution

ok, for my attempt at solving this I'll tell you what i was thinking. I look at this and think it must be inertia holding the block in, and i started thinking there must be something to do with energy in the question, but when i started with energy I realized that finding Vf would not help me know what the normal force at point Q is.

So after examining the question further I realized I'm not sure how to solve it, because if F=ma, and the block is decelerating (which a=9.8 i believe) then Vf gets me no where. But i know that the wall must exert a force on the block to keep it in the circle.

any help would be appreciated on how to solve normal forces in situations like this.

thank you.

2. Nov 5, 2007

### Kingrick

\ P ____T_______
\ / \
\ / \
\ / \
\ / \
\ | R |
\ | | |- Q
\ | | |
\ \ | /
\ \ | /
\ \ | /
_____\______|______/

try and picture this more circle like.

3. Nov 5, 2007

### Kingrick

ok my image does not work sorry

4. Nov 5, 2007

### stunner5000pt

draw an image using paint and attach it to one of your posts

5. Nov 6, 2007

### Jimmy Snyder

I'm guessing something like this. Can you clean this up Kingrick?
Code (Text):

\ P                ____T_______
\               /             \
\             /               \
\           /                 \
\         /                   \
\        |         R          |
\       |         |          |- Q
\      |         |          |
\     \         |         /
\     \        |        /
\     \       |       /
_____\______|______/

Cut and paste this into notepad or similar editor, fix it up, and then cut and paste it back into a reply. Don't forget to use the code tags as I have done.

Last edited: Nov 6, 2007