# Reaction force to resist rotation

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1. Sep 16, 2016

### MillyTheCat

1. The problem statement, all variables and given/known data
There is a object travelling at 0,2m/s with a mass of 75,000kg. The object impacts a fixed point at a distance of 3.5m from its center of gravity (COG) and rotates around this point. What is the reaction force at the point of rotation?

2. Relevant equations
I think it is something to do with momentum and rotational velocity equations. p = m x v and v = w x r, where w = rotational velocity (rads / s) and r = radius = 3.5m in this case. I know that w = 2 x pi x f (f = frequency) and force f = p / t (where t = time). But I'm not sure how to link it all together.

3. The attempt at a solution
So far the equations are all I have... applying rotational velocity to a momentum equation... how do I do that?

2. Sep 16, 2016

### rude man

So the object and the rotated mass are both 75,000kg?

3. Sep 18, 2016

### MillyTheCat

Yep that's correct. The object has a mass of 75,000kg and it rotates.

4. Sep 18, 2016

### Nidum

What the problem actually says is that the object as depicted by the blue rectangle is moving free until a point on the lower section impacts onto the corner of a fixed rigid block .

Implied is that before impact the object is moving on a horizontal path with it's long axis vertical and that there is no gravity force acting .

Last edited: Sep 18, 2016
5. Sep 19, 2016

### MillyTheCat

Hello Nidum, yes that is also all correct information. But any suggestions on what equations to use to calculate the reaction force?

6. Sep 20, 2016

### MillyTheCat

So, any tips on what equations to use or how to solve? :)