Magnetic force to hold machine and required Torque to drive

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Discussion Overview

The discussion revolves around the forces acting on a robot crawler equipped with a magnet, specifically focusing on the magnetic force required to hold the crawler against a vertical steel wall and the torque necessary to drive it upwards while overcoming gravity and friction. The scope includes theoretical considerations and mathematical reasoning related to forces and torque in a mechanical context.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • The initial post queries the magnetic force needed to hold the robot crawler against the wall and whether more force is required while it ascends.
  • The poster seeks to determine the torque necessary to drive the crawler upwards while countering gravity and magnetic force.
  • One participant questions how the robot can remain stationary or accelerate upwards given that friction and gravity act downwards, suggesting that static friction is at play.
  • Another participant clarifies that if the robot is not accelerating, the sum of the vertical forces (gravity and friction) must equal zero, implying that friction must act upwards to counteract gravity.
  • It is noted that if the robot accelerates upwards, additional friction is required to create a net upward force.
  • Participants discuss the role of the magnet as a horizontal force that contributes to generating friction necessary for the robot's movement.

Areas of Agreement / Disagreement

Participants express differing views on the direction and role of friction in relation to the forces acting on the robot. There is no consensus on the implications of these forces for the robot's ability to ascend the wall.

Contextual Notes

Participants have not fully resolved the implications of static friction in the context of the forces acting on the robot. The discussion also lacks clarity on the specific conditions under which the robot operates, such as the strength of the magnetic force and the coefficients of friction involved.

Chilu1234
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Homework Statement


The robot crawler has a magnet attached to it. The idea is to get the crawler up the wall.

What is the magnetic force required to hold a object (in this case) a robot crawler with an attached Magnet?
Is more magnetic force required to hold the crawler while it goes up the wall?

What is the Torque required to drive the robot crawler up the vertical steel wall while overcoming gravity and magnetic force.

Homework Equations


Sum of forces with x and y-axis is 0
and Torque based on Radius of wheel and friction force

3. The Attempt at a Solution

I have made a PDF file of the problem setup and variables and my solution.All formula I used is also there. I hope someone take a look at it and tell me if OK
 

Attachments

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If friction and gravity both act downwards, how can the robot stay in place or even accelerate upwards as those are the only external forces?
The robot is not sliding, you have static friction.
 
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@mfb .

Are you saying the friction acts in the same direction of wheel motion? I did not fully understand your comment. Please clarify. sorry for the trouble.
I am 100% that gravity acts downwards. But don't understand friction direction?
Also, there is a magnet attached to the robot that is suppose to pull the machine to the vertical steel wall.
 
There are two vertical forces acting on the robot: gravity and friction. If the robot is not accelerating, their sum has to be zero. Gravity is pointing downwards, so friction has to point upwards.
If the robot is accelerating upwards, the net force has to point upwards, so you need even more friction pointing upwards.

Chilu1234 said:
Also, there is a magnet attached to the robot that is suppose to pull the machine to the vertical steel wall.
That is a horizontal force only. It is necessary to get friction, of course.
 

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