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View Full Version : Physics question: How does a minibot climb the pole?

Techhexium
10-07-2011, 00:23
I am not in an FRC team but I have recently started to learn about physics. So far I have learned about Kinematics and Newton's Laws of Motion and forces. I have also followed up on FRC in the 2011 season (browsed the forums and watched the competitions) and I have been curious about how a minibot goes up in general. Can anyone describe to me how a minibot can climb the pole?
Thanks!
Ether
10-07-2011, 08:38
I am not in an FRC team but I have recently started to learn about physics. So far I have learned about Kinematics and Newton's Laws of Motion and forces. I have also followed up on FRC in the 2011 season (browsed the forums and watched the competitions) and I have been curious about how a minibot goes up in general. Can anyone describe to me how a minibot can climb the pole?
Thanks!

Assuming you already understand how a powered wheeled vehicle can accelerate on a horizontal surface, the difference in the case of the minibot is that a normal force must be created (to press the wheels against the pole) for a minibot to climb the pole. Is that what you are asking ?

This normal force is typically created in one of three different ways:

1) magnets

2) spring-loaded grip

3) gravity acting on the center-of-mass of the minibot, creating around a pivot point a torque which presses the minibot against the pole
DonRotolo
11-07-2011, 11:12
...and of course the 'upwards' force is greater than the 'downwards' force due to gravity.
Bob Steele
11-07-2011, 12:21
In point of fact, the pole pushes the robot up.
Newton's third law...

A force generated by the minibot in the vertical direction ("Down") results in a paired reaction force from the the pole on the robot in the opposite ( "UP") direction.
Techhexium
11-07-2011, 13:49
Thanks for the responses everyone!

In point of fact, the pole pushes the robot up.
Newton's third law...

A force generated by the minibot in the vertical direction ("Down") results in a paired reaction force from the the pole on the robot in the opposite ( "UP") direction.

I believed that the way the minibot climbs the pole is similar to how a car goes forward because in both situations the wheels of both a car and a minibot exert a force to the road or the pole. The opposite force makes both move, but the two forces don't cancel each other.


Assuming you already understand how a powered wheeled vehicle can accelerate on a horizontal surface, the difference in the case of the minibot is that a normal force must be created (to press the wheels against the pole) for a minibot to climb the pole. Is that what you are asking ?



Yes, that was what I was wondering about. I understand that a normal force keeps the minibot on the pole but I wasn't able to determine how that worked.

...and of course the 'upwards' force is greater than the 'downwards' force due to gravity.

I'm not sure if gravity causes the 'upward' force to be greater. The upward force would have to be greater for the minibot to go up, but the downward force is the weight of the robot which is made up of mass times gravity so the upward force needs to overcome gravity.
Ether
11-07-2011, 16:26
...and of course the 'upwards' force is greater than the 'downwards' force due to gravity.

Only when the minibot is accelerating :-)
DonRotolo
11-07-2011, 18:15
Only when the minibot is accelerating :-)
Well, he did ask how it climbs the pole. If a=0 then it won't move from a standstill. But we're splitting hairs. Hares? (http://www.nonstick.com/sounds/Witch_Hazel/ltwh_011.mp3)
(Bonus points if you know the reference)
Ether
11-07-2011, 18:35
Well, he did ask how it climbs the pole. If a=0 then it won't move from a standstill.

... unless it was track-launched and Vo>0 :-)
EricH
11-07-2011, 19:28
... unless it was track-launched and Vo>0 :-)



Until Vo runs out due to g acting on it--which, I suppose, is why motors were required in the first place. :p
Ether
11-07-2011, 19:47
Until Vo runs out due to g acting on it--which, I suppose, is why motors were required in the first place. :p

You missed the point. So much for my attempt at geek humor.

Vo won't "run out" if the vertical component of the reaction force of the pole on the minibot is equal to g.
Molten
12-07-2011, 02:34
You missed the point. So much for my attempt at geek humor.

Vo won't "run out" if the vertical component of the reaction force of the pole on the minibot is equal to g.




I understood the implication but figure that a proper explanation is in order for the OP to learn.

If the force acted upon the robot in the upward direction is equal to the force due to gravity, the robot will go at a constant velocity. The Vo that was mentioned is the initial velocity of the robot. In other words... if you start the robot at 1 m/s and the forces are equal the robot will continue at 1 m/s without ever slowing down or accelerating.

Jason
Ether
12-07-2011, 13:32
...and of course the 'upwards' force is greater than the 'downwards' force due to gravity.

I'm not sure if gravity causes the 'upward' force to be greater. The upward force would have to be greater for the minibot to go up, but the downward force is the weight of the robot which is made up of mass times gravity so the upward force needs to overcome gravity.

Don was not saying that the "upwards force" is greater than the "downward force", due to gravity.

He was saying that the "upwards force" is greater than the "downward force due to gravity".


Gotta love the English language.