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Question for you.

UglyCasanova

UglyCasanova

Lifer
Ok, my physics teacher says we have to figure this out by tommorow. It is a very low level class so it should be easy for all of the genius's on ATOT 😀.

A donkey is pulling a man in a cart. The donkey turns and says to his master, "This is futile. According to Newton's 3rd law, whatever force I excert on the cart, the cart excert's on me. It is impossible for us to go anywhere." Where is the flaw in the donkey's theory?


And no it's not that donkey's don't talk. 😀
 
Uhm, the donkey misses that the reciprocating force exerted does not necessarily act on the original force in the equation, that is, the donkey's efforts go into turning the wheels of the cart, there is a transfer of the work.
 


<< Uhm, the donkey misses that the reciprocating force exerted does not necessarily act on the original force in the equation, that is, the donkey's efforts go into turning the wheels of the cart, there is a transfer of the work. >>



So the "equal and opposite force" is not neccesarily friction or whatever pulling back on the donkey. It is transfered into the wheel? I thought I remember though that Frictional Force = - Applied Force
 


<< Uhm, the donkey misses that the reciprocating force exerted does not necessarily act on the original force in the equation, that is, the donkey's efforts go into turning the wheels of the cart, there is a transfer of the work. >>



also, the cart-donkey system would be considered as one total "thing", and the newtons 3rd law equation would only be applying to internal forces of the system, not on the whole system moving
 
the donkey is correct... if you live in a vacuum 😛 of course, then your donkey would explode... we wouldn't want that.
 


<< the donkey is correct... if you live in a vacuum of course, then your donkey would explode... we wouldn't want that. >>



So....with the absence of air both forces would counter-act one another to where you wouldn't be able to move? How does the inclusion of air affect it?
 


<<

<< Uhm, the donkey misses that the reciprocating force exerted does not necessarily act on the original force in the equation, that is, the donkey's efforts go into turning the wheels of the cart, there is a transfer of the work. >>



So the "equal and opposite force" is not neccesarily friction or whatever pulling back on the donkey. It is transfered into the wheel? I thought I remember though that Frictional Force = - Applied Force >>



frictional force = - applied force when an object is moving at constant velocity
 


<< Doesn't the wheel provide a mechanical advantage? >>



Mue is decreased, but I believe that is all. I am sure it would be the same problem if he was pulling a big rock.
 
A simple answer is:

When the donkey excerts a force on the cart, the force is transfered into torque at the wheels, and in a perfect world (frictionless axle) the wheels would exert the same for on the ground causing the cart to move.

hmmm, Axle... Axle F...


*off to find AxleF remixes*
 


<< What does Ff = when the object is accelerating? >>



Fnet=ma
Fdonkey - Ff=ma
so :

- Ff =ma - Fdonkey

mass being htat of the total system
 


<<

<< the donkey is correct... if you live in a vacuum of course, then your donkey would explode... we wouldn't want that. >>



So....with the absence of air both forces would counter-act one another to where you wouldn't be able to move? How does the inclusion of air affect it? >>




well in the absence of *everything* other than the donkey and the cart. that is what i meant by vacuum. but this will never happen, trust me 😛
 


<<

<<

<< the donkey is correct... if you live in a vacuum of course, then your donkey would explode... we wouldn't want that. >>



So....with the absence of air both forces would counter-act one another to where you wouldn't be able to move? How does the inclusion of air affect it? >>




well in the absence of *everything* other than the donkey and the cart. that is what i meant by vacuum. but this will never happen, trust me 😛 >>



cause gopunk will always be there
 
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