Newton third law. Is there a limit on how much force you can apply to an object? Recently in class we went over Newton's Third Law. In the book they put an example of hitting a punching-bag with your fist and hitting a piece of paper, or an object with much less mass. It's clear that you cannot exert more force on the paper than what the paper can exert on you, otherwise it might stop your fist in the process, just like the punching-bag stops your fist. Is there a limit, however, on much force you can exert on a paper? This might sound silly but it got me thinking for the past couple of days. 
In order to make it a little more clear consider a Car with a paper in front of it. The car-system can continuously increase the acceleration, but this means that the paper will increase the acceleration as well. Ergo, by Newton 2nd Law, the force exerted on the paper has to increase. Right? That same force back to the car. Therefore, the car can continuously increase the force it exerts on the paper. 
 A: There is no such limit.
Note that hitting something is a bad example for explaining about force: the impact is very short, so you get a short burst of strong force, but it's hard to say how much exactly. In an idealised sense, the force is in fact infinite for any such hit – but only for an infinitely short time!
A car with a piece of paper in front of it is better. Here, the force is indeed limited, but not by anything fundamental but just by the car's ability to accelerate. If the car was able to accelerate arbitrarily rapid, the the force could indeed become as big as you want – however, since the car has so much more mass than the paper, the internal forces in the car would always be greater by that factor as well, so any noteworthy-sounding force on the paper would mean you'd rip the car itself apart.
A: Many confuse force with pressure. Because of close interaction of force with mass and acceleration it is not very intuitive to see that.
Imagine that piece of paper resting on the surface of a planet with huge gravity: there is no limit to the force exerted on the paper by the reaction of it's weight by the surface of planet. It could possibly crumble into itself and tear apart.
The car example is not a good example for this case. Acceleration of most cars are limited by the friction of their tires and is usually in the order of one G, which is not significant. Even the most powerful rockets don't offer accelerations of more then 12-20 G.
But if you had your car with the paper attached to its front bumper get into a frontal collision the force on the paper would be huge enough to disintegrate it.
