# What is the minimum mass of the barbell without tipping?

1. Nov 21, 2016

### Luke0034

1. The problem statement, all variables and given/known data
Typical weight sets used for bodybuilding consist of disk-shaped weights with holes in the center that can slide onto 2.20 m long barbells. A barbell is supported by racks located a fifth of its length from each end, as shown in the figure. What is the minimum mass m of the barbell if a bodybuilder is to slide a weight with = 22.0 kg onto the end without the barbell tipping off the rack? Assume that the barbell is a uniform rod.

2. Relevant equations

sum of all torques = 0

3. The attempt at a solution

I tried to make the the intersection of the barbell and the left rack the pivot point. Then I found the torque of the weight, the center of mass of the bar, and then the 2nd rack, but I came out with the wrong answer. I think I'm on the right track on how to do it, but I'm not sure where I'm messing up. Explanation would be helpful... studying for an upcoming test. Thanks!

2. Nov 21, 2016

### BvU

1. Make sure the problem statement is complete. What about the mass of the bar ?
2. show your calculation work in detail

Good luck !

3. Nov 21, 2016

### Luke0034

I'll try to find the page I did this on, but the mass of the bar is what I'm trying to find.

4. Nov 21, 2016

### Luke0034

Never mind, I got the answer myself haha.

5. Nov 21, 2016

### Staff: Mentor

Can you provide the mass of the bar so others can work the problem if they come across this thread?