# Urgent - Loop de Loop problem, Normal Forces

1. Oct 18, 2013

### gcharles_42

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

In Fig. 8-28, a small block of mass m = 3.0 kg can slide along the frictionless loop-the-loop. The loop has radius R = 0.80 m. The block is released from rest at point P, at height h = 2.9R above the bottom of the loop.

I attatched a picture

(a) Find the speed of the block when it reaches point Q.

(b) Find the normal force on the block at point Q.

(c) Find the normal force on the block when it is at the very bottom.

(d) Find the normal force on the block when it is at the top of the little loop (i.e., at a height 2R above the ground)

2. Relevant equations

KEi + PEi = KEf +PEf

KE=1/2mv^2

v = w (r)

3. The attempt at a solution

So for the velocity isnt it just converting the PE at the top for the KE at the bottom?

For all the normal forces i am completely stumped

#### Attached Files:

• ###### Screen Shot 2013-10-18 at 4.44.08 PM.png
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2. Oct 18, 2013

### gcharles_42

So for a) v = 3(.98) 1.9(.8) = 1/2(3)v^2

3. Oct 18, 2013

### tiny-tim

hi gcharles_42!
yes

but i don't understand the LHS of your equation
for the normal forces, you need to use Ftotal = ma in the normal direction

(you'll need the centripetal acceleration formula)