# Calculate the Initial Calue of the Force at the Bearing

1. Apr 25, 2013

### Northbysouth

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

The uniform slender bar is pivoted at and swings freely in the vertical plane. If the bar is released from rest in the horizontal position, calculate the initial value of the force exerted by the bearing on the bar an instant after release.

I have attached an image of the question

2. Relevant equations

3. The attempt at a solution

I'm honestly not sure how to start this question. I'm pretty sure that this is a straightforward question

I think I may need to use the equation:

ƩMO = IGα + maGd

Any advice would be appreciated. Thank you

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2. Apr 25, 2013

### Northbysouth

Ahh, wait I've figure it out now.

I used the fact that:

ƩMO: IGα = -mg(L/2)

Solving for α = -mg(0.5L)/IG

where L is the length of the bar

Then I applied a normal and tangential coordinate system, with t pointing downwards and n pointing towards O.

ƩFt: mrα = Oy - mg

Plugging in the formula that I solved for α above I get

Oy = mr[-mg(0.5L)/Ig] + mg

My final answer was 88.29 N