# What force is the pin exerting on the rod?

#### AirJersey

A thin rod of uniform mass M and length L is attached to a string at one end to the ceiling and a pin at the other end to the wall. The rope (connecting the ceiling and the horizontal rod) is cut at t = 0 s.

1) What is the force of the pin at t = 0 seconds?

2) When the rod swings vertically, what force is the pin exerting on the rod?

3) When the rod reaches the vertical part of its swing, what is the rod's angular speed and angular acceleration?

4) If the initial position of the rod was almost vertical, what would be the force of the pin when it has reached horizontal position.

L/2 mg sin90 = I $$\alpha$$

I got force of pin for the initial condition = mg/4 and tension of rope = mg/2. A t=0 accerlation of center of mass I got -3/4g. All the above questions I have no idea how to set up.

#### ideasrule

Homework Helper
Re: Rotation

Start with a free-body diagram. You will find that you need a relationship between the angular speed of the rod and how much it rotated by. No problem: use the conservation of energy.

### The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving