I've got to get out of the 700 Club. Here's another Physics ...

[Crazy Guggenheim]

question. According to Newtons 3rd Law if there is an object M1, that exerts a force on another object M2, then there is an equal and opposite force exerted on M1. If this is true than how can objects move? So if you push a cart and the cart exerts the same force back ay you then why does the cart move?

[billyskank]

1. Simple

So, both you and the cart are experiencing equal (in magnitude) but opposite forces, right? If both you and the cart were situated on a frictionless surface (or in space) then you would both move away in opposite directions, with equal (in magnitude) momemtum.

However, mostly when you push a cart, you have more friction on your feet than the cart does on its wheels. Unless its brakes are on. Or it is up against a wall. Otherwise, the force the cart exerts on you is balanced by another equal but opposite force exerted by your shoes/feet/legs, and so the cart moves, but you don't.

[Crazy Guggenheim]

2. But the forces would still be the same.. Eq and opposite. So why

would any of them move?

[billyskank]

3. The point of action is where your hand touches the cart

At that point, the cart is experiencing a force directed away from your hand. Simultaneously, you are experiencing a force directed away from the cart. So, in the absence of any other forces, it is not that neither of you will move, but rather that both of you will move. Away from each other.

[Crazy Guggenheim]

5. I thinkit has to do with the direction of Momentum.

[billyskank]

7. The momentum goes whichever way the forces go

Try to answer your own question. Why do you think that the cart shouldn't move?

[billyskank]

4. Think of it this way

Is it that you are pushing the cart, or is the cart pushing you? In actual fact it makes no difference which way round you consider it, because in truth, each of you is pushing the other.

[Robb]

8. Bingo

Both of you will move, but whichever has the least amount of friction going on will move the most -- e.g., the one with wheels. :)

[kick-ass-bob]

6. Sorry - I see M1 and M2 and all I think is

Money Supply.