# Challenging problem

1. Nov 3, 2008

### Pakbabydoll

1. The problem statement, all variables and given/known data
n my homework we are asked to find the magnitude of the reaction force at the pivot at a instant and earlier in the problem we found the magnitude of the angular speed at one instant, the magnitude of the angular acceleration at the same instant, and the magnitude of the acceleration of its center of mass at the same instant

PROBLEM # 13

2. Relevant equations
I am lost now.... am attaching the picture

3. The attempt at a solution
F= (4.5)(16.43509961) (my numbers)

than I tried
F= ma
F= (4.5)(7.350000002) (transitional acceleration only)

my numbers =

angular acceleration= 2.133526851
angular velocity= 2.065684802
Net acceleration= 16.43509961

mass- 4.5
rod- 6.89

What am I doing wrong?

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Last edited: Nov 3, 2008
2. Nov 3, 2008

3. Nov 4, 2008

### Pakbabydoll

so so for future users this is how you get the answer:

(1/2)(9.8)(m)^2+(1/4)(9.8)(m)^2
than take square root of that

but I still don't know why you get it that way.... its too late for me to plug it in to the system so I am not sure if its even right but thats how you get it....

4. Nov 4, 2008

### Staff: Mentor

On the right track here. Note that F is the net force. You need to find the force of the pivot on the rod.