Push Pull Physics
Why is it easier for the horse to pull the cart than tovpush it??
It's not easier for the horse, it's easier for the guy who arranges the
mechanism by which the horse drives the cart. If the horse pulls, you
can use a rope. If the horse pushes, you need something rigid, like a
bar. You also need to make sure the force gets exerted through the
cart's center of mass (otherwise the cart will try to flip over), and
this means you have to align the bar. A rope is self aligning; tension
will always try to align it along a line from the point at which the
pulling force is applied through the center of mass of the cart.
Probably for two major reasons:
1. It is easier to harness the horse to the cart in a comfortable way
if the horse is in front. This could probably be overcome with
the proper technology.
2. It is easier to control the direction the cart will go in if the
cart follows the horse.
Having said this, I'm pretty sure I could design a cart which would
work adequately with the horse behind. It would probably involve a
pair of stiff rods extending behind the cart with normal soft
harnessing to the horse. The rods would have to be pivoted to allow
the cart to turn without pushing the horse sideways. The cart would
probably be steered by a steering wheel which turns the front wheels
and is controlled by the driver.
The physics is the same in the two cases. For example the force
exterted by the horse for a given speed on a given hill would be the
same in the two cases.
Since I've never seen a cart with the horse behind, there must be good
reasons (such as above) for putting the horse in front. I could
imagine putting the horse behind in a war cart to protect the horse.
This has to do with control rather than the amount of work being done. Think
about how you would direct something that you were pushing in front of you.
If it starts to go in the wrong direction and you just keep pushing it goes
even further in the wrong direction. If you're pulling in the right
direction the cart can't go very far in the wrong direction.
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Update: June 2012