Mechanical Physics Question.

[PhilDawson8270]

@nickyboy and @Yellow Saddle are correct with their answers.

The phrasing of the original post was confusing, but I have read it through a few times, they're spot on in my opinion.

 

[Piemaster]

 

[Yellow Saddle]

[QUOTE 4150855, member: 9609"]Obviously - but that does not answer my question, I will try again.

if it would take a 50kgf push to the rear of the vehicle to overcome the coefficient of rolling resistance, how much torque would you have to apply to the centre of the wheel to initiate movement. ? would it be 50kg x the radius of the wheel.[/QUOTE]
500NM

 

[Chromatic]

[QUOTE 4150855, member: 9609"]Obviously - but that does not answer my question, I will try again.

if it would take a 50kgf push to the rear of the vehicle to overcome the coefficient of rolling resistance, how much torque would you have to apply to the centre of the wheel to initiate movement. ? would it be 50kg x the radius of the wheel.[/QUOTE]

As Yello Saddle says: 500NM.
Unless you are using the wheel to apply the force it doesn't matter what the radius of the wheel is. If you are using the the wheel then it would be 50 kg at the wheel outer IF the wheel was 1 meter radius.

 

[TVC]

Special prize to the first person to tie gravitational waves to the variation on force required.

 

[Chromatic]

[QUOTE 4150700, member: 9609"]torque is not dependant on length of lever, but obviously a longer lever allows higher torque at lower effort[/QUOTE]


Yes it is. For a given force, say 10 N, applied to a lever 1 meter long the torque is 10Nm.
The same 10 N force applied to a lever 2 meters long (ie twice as long) give a torque of 20Nm, ie twice the torque.

 

[Yellow Saddle]

[QUOTE 4150855, member: 9609"]Obviously - but that does not answer my question, I will try again.

if it would take a 50kgf push to the rear of the vehicle to overcome the coefficient of rolling resistance, how much torque would you have to apply to the centre of the wheel to initiate movement. ? would it be 50kg x the radius of the wheel.[/QUOTE]

Just a small point. You need to remove the word coefficient here to make sense. You simply want to overcome the rolling resistance, not it's coefficient.

 

[Levo-Lon]

Sounds like its going to be a tight wheel nut to me..

 

[vernon]

The force required to move the car is 500N. Irrespective of the diameter of the wheel the force applied to the end of a torque wrench whose length is the radius of the wheel and tyre and is affixed to a central nut will be 500N Assuming 1kgf to be 10N

The as the torque wrench is extended beyond the radius of the tyre then the force required will reduce because the the moment has increased.

The steps to solving the problem is to regard the moment resisting rotation to be equal to the force need to make the car move x radius of wheel and tyre and be the anticlockwise moment. The clockwise moment applied by the torque wrench at the radius of the wheel and tyre will be equal and opposite to the anticlockwise moment at the point at which motion just commences.

Anti clockwise moment######= Clockwise moment
Resistant force x wheel radius = Torque wrench force x wheel radius

At this point you can cancel out the wheel radii and demonstrate that:

Resistant force = Torque wrench force

Furthermore since the anticlockwise moment is expressed in Nm and is a constant it is also the torque required to turn the wheel irrespective of the length of the torque wrench seeing that the clockwise moment must also be constant.

What will change is the force applied to the end of the torque wrench as its length changes.

Shorter than wheel radius then the force increases.

Greater than wheel radius then force needed decreases.

End of arguments.

 

[Levo-Lon]

Nice one @vernon ,i understand that..sort of

 

[Chromatic]

[QUOTE 4150975, member: 9609"]Obviously it is, I have never said otherwise. the way you quoted me puts my answer to another post out of context, as I said "a longer lever allows higher torque at lower effort"[/QUOTE]

You also said 'torque is not dependent on length of lever'...

Following 'torque is not dependent on length of lever' with 'but obviously a longer lever allows higher torque at lower effort' is contradictory.

 

[Chromatic]

The force required to move the car is 500N. Irrespective of the diameter of the wheel the force applied to the end of a torque wrench whose length is the radius of the wheel and tyre and is affixed to a central nut will be 500N Assuming 1kgf to be 10N

The as the torque wrench is extended beyond the radius of the tyre then the force required will reduce because the the moment has increased.

The steps to solving the problem is to regard the moment resisting rotation to be equal to the force need to make the car move x radius of wheel and tyre and be the anticlockwise moment. The clockwise moment applied by the torque wrench at the radius of the wheel and tyre will be equal and opposite to the anticlockwise moment at the point at which motion just commences.

Anti clockwise moment######= Clockwise moment
Resistant force x wheel radius = Torque wrench force x wheel radius

At this point you can cancel out the wheel radii and demonstrate that:

Resistant force = Torque wrench force

Furthermore since the anticlockwise moment is expressed in Nm and is a constant it is also the torque required to turn the wheel irrespective of the length of the torque wrench seeing that the clockwise moment must also be constant.

What will change is the force applied to the end of the torque wrench as its length changes.

Shorter than wheel radius then the force increases.

Greater than wheel radius then force needed decreases.

End of arguments.

Nearly all this has been said in one from or another in this thread already.

 

[vernon]

Nearly all this has been said in one from or another in this thread already.

It is a neat one stop shop.

 

[Chromatic]

[QUOTE 4150995, member: 9609"]yes it appears contradictory, because the first part was in answer to someone who said "Torque required depends on the length of the lever"[/QUOTE]


Ah, I see that now, apologies.

 

[GM]

@User9609 can you post another bird nest thread, far more interesting!