 #1
Towelie
 5
 0
[SOLVED] Force needed to make a disk climb a step
Howdy ho. First off, let me say that I'm a newbie here, and I'm not sure if this is the correct place to put this doubt. Here's the deal:
We have a disk, and we need to know the force F needed to have it climb the step, with 50mm. The force is applied at the top of the disk.
...F < ...
.........
........
___________...
...50mm  ...
....___..._______
Sorry for that draw, it's the best I could do.
The only known data is:
the step has 50mm;
the disk is uniform and weights 40N;
no friction is to be considered.

I've tried solving it in several ways. I've considered a normal vertical reaction 1 between the ground and the disk, and considered a normal diagonal reaction 2 between the disk and the tip of the step. I also considered that the angle this reaction 2 makes is 45º. So, I concluded that, in the vertical axis, we have: 40 = N1 + N2.sin45º.
After this, we would have in the horizontal axis the force F and N2.cos45º. I thought that one condition for the disk to climb the step would be: F > N2.cos45º.
However, this wouldn't be enough. So I used the moment. The moment the force F causes in the center of the disk is F.r . We do not know r, so this would lead to another variable in another equation. So, unless there is missing some data here, I don't know how to solve it. I have the solution, and it says the force should be F=17,88N .
Sorry for any language error, english is not my native language, and is not the language I'm using in classes, so I may have mistaken some technical terms.
Howdy ho. First off, let me say that I'm a newbie here, and I'm not sure if this is the correct place to put this doubt. Here's the deal:
Homework Statement
We have a disk, and we need to know the force F needed to have it climb the step, with 50mm. The force is applied at the top of the disk.
...F < ...
.........
........
___________...
...50mm  ...
....___..._______
Sorry for that draw, it's the best I could do.
The only known data is:
the step has 50mm;
the disk is uniform and weights 40N;
no friction is to be considered.
Homework Equations

The Attempt at a Solution
I've tried solving it in several ways. I've considered a normal vertical reaction 1 between the ground and the disk, and considered a normal diagonal reaction 2 between the disk and the tip of the step. I also considered that the angle this reaction 2 makes is 45º. So, I concluded that, in the vertical axis, we have: 40 = N1 + N2.sin45º.
After this, we would have in the horizontal axis the force F and N2.cos45º. I thought that one condition for the disk to climb the step would be: F > N2.cos45º.
However, this wouldn't be enough. So I used the moment. The moment the force F causes in the center of the disk is F.r . We do not know r, so this would lead to another variable in another equation. So, unless there is missing some data here, I don't know how to solve it. I have the solution, and it says the force should be F=17,88N .
Sorry for any language error, english is not my native language, and is not the language I'm using in classes, so I may have mistaken some technical terms.