I need a little understanding regarding Physics, Two Questions

[Luckey]

Question 1:
If newton's third law states that there is always an equal opposing force, then why is it that a sledgehammer can break through a table? The table couldn't withstand the same force so it breaks. Doesn't that contradict the law?



Question 2:

In the picture it displays a man throwing a chair through a wall. In reality would this even be possible? Doesn't Newton's third law suggest that with every force there will be an equal and opposite reaction? How can you justify a chair with less durability then a solid concrete wall going through a wall? Even if the chair were to accelerate at 5,000+ mph, would it not just break to pieces before breaking through the wall since it is made of less compact molecules?

[Nessus]

Your second questions answers your first, a sledgehammer is stronger than a table. And in the picture the chair goes through some glass.

[JavaTool]

Newton's third law is related to the conservation of momentum - it states that no momentum is gained without an appropriate loss of momentum. The table does indeed withstand the force by "pushing" back with an equal and opposing force, but this does not mean that object cannot break - an object not feeling the effects of a force is impossible, as that implies that work was just "lost" on the object. Instead, what happens is that force is applied to the table, causing it to break up as the energy causes the particles to fly apart from each other, but there is also an equal and opposing force that is exerted upon the hammer that causes it to stop eventually. There does not have to be an immediate opposing force that stops the hammer totally, but only a local opposing force against the hammer particles that are actually exerting a force on table particles.

For an intuitive understanding of the third law of motion, consider how when you touch/apply force to an object, you feel a pressure - the object is pushing back with an equal and opposing force. If you maybe have super-strong hands, you might be able to push it hard enough that the object breaks - but there is a corresponding increase in pressure.

Something tells me I'm not being crystal-clear, so feedback is appreciated.

[Luckey]

Are you saying that since the durability of a chair is less than that of a wall it will break before going through the wall? I've heard instances of a straw going straight through a tree in hurricanes. Doesn't the durability matter? Basically what i'm getting at is, if there was a chair thrown at great speed (let's say 5,000mph), would it go through the wall, or would it completely shatter against the wall?

[Nessus]

Its safe to say that the kinetic energy of a chair (approx 5Kg) going at around 5000 miles per hour would be enough to completely demolish the wall (the KE of the chair is equivalent to nearly 3 Kg of TNT).

If material A is stronger than material B then B would be able to withstand larger forces before breaking/deforming than material A.

Just because the chair has enough energy to get though the wall, doesn't mean the chair will be fine after its passed though the big gaping hole.

[Schneibster]

Worth noting that straws are quite surprisingly strong along their length. And because they're hollow, their open ends are relatively sharp; but like a cookie cutter, not like a knife. So when they get going a few hundred miles an hour in a tornado, they can cut into wood and stick in a wall or a tree. Bet you never see any stuck in concrete or steel, though!