according to newton's first law, when enough horizontal force is applied to a penny to slide it across a table

Question

continued from the other question: the penny will slide to the edge of the table and fall off..However, if the force applied is not strong enough, the enny will stop on table.the force that stops the penny is

a. gravity
b.friction
c.air
d.force of the table

and can u give me a defense for it

Answer 1

The answer is not given by any of the choices, although friction is the best answer. Gravity is perpendicular to the motion of the penny and has no effect on it. Friction is not a force, but an opposition to force. The electrostatic force creates friction. Force, according to Newton, is given by the formula: F=ma. When you push the mass of a penny, you accelerate it, creating a force. Friction has no mass that can be accelerated. Air is a fluid and easily gives way to solids. The force of the table is in opposition to the force of gravity (they are called "force pairs") and is perpendicular to the motion of the penny. As for a defense for it, no, I am not a Physicist, I am a Geologist.

Answer 2

Well, obviously, if the force from each team were equal, *neither* would win. It would end in a draw. In order for one team to win, the "net" force (on the rope at least) cannot be zero. One team MUST have more force than the other to avoid a draw! But how is this possible, under Newton's Third Law!? The tricky part is that while forces do, indeed come in equal, opposing pairs, Newton doesn't specify exactly "who is pushing who." It's not always clear where those pairs occur! To understand this better, let's say that instead of teams, two racecars are pulling at the ends of the rope. What happens when we suddenly cut the rope with a big pair of scissors? Each racecar is then pulling against.........what? Pulling against *Nothing*, are they? Actually, what's important here is that the cars' tires are pushing against the *Earth*, and the Earth pushes back in an equal and opposite way. This explains why the cars would quickly accelerate down the road once the rope is cut. To be more specific, the Third Law is a statement of "Conservation of Momentum," not conservation of force. The exact wording is "for every action there is an equal and opposite....." not "for every force." A consequence of this is that the total of ALL the forces in a system must zero, but the total of SOME of the forces doesn't necessarily need to be! The force the two team apply on the rope isn't ALL the forces in the system, so one team may be able to apply more force than the other. But once you also add up the force that the Earth applies to the feet each team, plus the force that the teams apply to each other, the result is indeed zero. Considering only the forces on the rope, isn't considering the the whole system. ~WOMBAT

Answer 3

b... friction.....

nope..........but I'll bet your book can.............