# Homework Help: Torque calculation

1. Oct 26, 2015

### balan turer

Hi everyone,

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

In the picture in attachment you can see 2 objects: "1" (it would be a door keeper) is able to move in direction "Y", "2" (it would be a lock latchbolt) is able to rotate around its axis. The 2 objects are in contact with each other. On the object "1" we have a constant applied load of 10 N. The question is: how much is the required torque to rotate the object "2" in the both directions with/without considering friction (coefficient of friction = 0,25)? At this moment I wouldn’t consider neither the object masses nor the gravity.

2. Relevant equations

-

3. The attempt at a solution

-

Please post here below if you need any clarification!

#### Attached Files:

• ###### Untitled.jpg
File size:
19.8 KB
Views:
93
Last edited: Oct 26, 2015
2. Oct 26, 2015

### BvU

Hello balan, welcome to PF !

If your post wasn't moved here from another forum, you must have seen the homework template flash by. And deleted it by accident. It is very useful however, and even mandatory in these PF forums. So indulge us and complete your post, please.

I, for one thing, wonder about the completeness of the problem statement. What are the objects (a ring, a sphere, a solid cylinder); how about gravity ? etcetera.

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

2. Relevant equations

3. The attempt at a solution

3. Oct 26, 2015

### balan turer

Hello BvU,

Regards

4. Oct 27, 2015

### balan turer

Hi guys!

Any idea? :)

5. Oct 27, 2015

### BvU

Did I post this for nothing ? The idea is that you do something and then we'll help you !

6. Oct 27, 2015

### BvU

So is this homework or a hobby project at home ? After your edit of the first post at least we know we don't worry about gravity.
And a lock latchbolt can usually slide and not much more -- except rotate around its length axis if it is round; that means the rotation axis in your picture is fixed ? If so, object 1 can't move further in the y direction than shown.

If it can move in the direction of the tangent at the point where it touches the bolt, then it can rotate the cylinder, provided there is friction. No friction means no tangential force, so no angular movement.

If you had something else in mind, we'll need some more explaining !

7. Nov 9, 2015

### balan turer

Well, a better explanation could be that it is similar to a braking system. The "1" object (called keeper) is free to move along the Y-axis, whereas the "2" object (called latchbolt) can rotate around its fixed rotation axis, as you suppose in your post. The question is that if the keeper is pushed by a given load ( in this case its magnitude is 10 N and its direction is along the Y-axis), how much will be the torque to rotate the latchbolt in the clockwise/anticlockwise directions?

First of all I think it would be better to determine the acting forces, their direction and magnitude (my attempt you can see in the attached figure). Do you agree with it?

File size:
28.3 KB
Views:
80
8. Nov 9, 2015

### BvU

Well, to be honest I still don't have a good idea what this all is. Must be my non-native english that's preventing me (a keeper is a guy who tries to keep the ball out of the goal net ). Where is the door, where does the keeper come from ? I can read the red 10N, the x, the FIXED and the force decomposition (but not the subscripts). Where would the 5.77 N come from ? I don't see any movement in object 1; or is there a hidden something that pushes it from the left ?

9. Nov 9, 2015

### balan turer

The real problem must be my english, not yours.. ;) However, the object 1 we can call counterstrike, insert, keeper, etc, etc as well... In this simplified case the keeper is fixed on a hinged door (and I also assume that the door don't rotate around its hinges but moves in y-axis direction) and the lock (with its latch) is on the doorframe, but obviously in reality the lock should be on the door.. Object 1 is able to translate until touching object 2. After that, it will transmit the load of 10 N to object 2. If the angle is 30°, we can find the resultant force's magnitude wich is 11,55 N pointing in the rotation axis of object 2. But I have some doubt about the direction and the magnitude of the other force-component.. In your opinion it could be of 5,77 N pointing in the x-axis direction?