a horse pulls a heavy cart with a certain force. the cart, in turn, pulls back with an opposite but equal force on the horse. doesnt that mean the forces cancel one another, making acceleration impossible? yes or no.
2007-05-25 10:01:03 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Someone just asked this:
Tell your lazy horse you didn't buy him shoes for no reason, so stop making excuses, get off his lazy @ss and push off on the ground so that the reaction of the earth on him equals or exceeds the reaction force from the cart so he can go on forward.
Moral of the story: don't try to teach horses physics.
2007-05-25 10:03:43 · answer #1 · answered by Anonymous · 0⤊ 0⤋
f = ma; where f is net force acting on the system (horse and cart), m is the mass of the system, and a is its acceleration.
From your description, the forces are equal and opposite; so they add up to f = 0 = ma and since m > 0 that means a = 0; acceleration is zero.
But, and this is a BIG BUT, that does not mean v = 0. In fact, that horse could very easily be pulling that cart along at, say, 2 - 3 mph. Why is this? Because once a body is in constant motion it'll stay in motion (v > 0) until a net force changes that motion. But we've already established the net force is f = 0; so there is no force to change that motion. My point is this, that horse may not be lazy after all, she may be doing her job and expending kinetic energy KE = 1/2 mv^2.
Thus, all three of Newt's motion laws have been invoked: mv, f = ma, and f = 0, which are, respectively, inertia (v = constant without force), force causes acceleration, and sum for equal/opposite forces is zero when a = 0.
2007-05-25 17:54:03 · answer #2 · answered by oldprof 7 · 0⤊ 0⤋
No. The horse pulls the cart with more force than the opposite, UNEQUAL force of the cart, therefore the cart moves. The horse uses energy, but the cart doesn't. Unless gravity (a steep hill?) or some other force overpowers the horse's forward motion, the cart moves!
2007-05-25 17:07:02 · answer #3 · answered by Spotbox 1 · 0⤊ 3⤋
yes. it's newton's second law, the law of basically force. if the horse had a force of 50, and the cart 40, then the cart due to a certain weight which would add more force, would move.
2007-05-25 17:05:59 · answer #4 · answered by love in siberia 6 · 0⤊ 1⤋
no, if the force is enough to move the cart and overcome its friction and inertia then it is unbalanced and becomes accelertaion, once in motion on a level the horse only needs to overcome friction to stay in motion.
2007-05-25 17:14:42 · answer #5 · answered by pechorin1 3 · 0⤊ 0⤋