Newton's first law says that "Objects in Motion stay in motion unless acted upon by an unbalanced force" That explains why when I drive along in a car, I can throw a ball directly up in the air it comes straight back down into my hand. Gravity Made it fall, but Newtons first law explains why it moved forward at the same rate as the car. Newton says the object had horizontal motion nothing changed that so It continued at the same speed as the car in the horizontal direction. To me that is an description of what has happend but it is not an explaination. Why when in mid air does it retain this forward motion? In your hand it is directly in contact with the car. So it is acted upon by a forward force due to the car engine, A normal reaction from your hand, gravity and possibly friction forces from your hand. In mid air the only forces acting upon it is the force of gravity and air resistence. These do not affect horizontal motion. There is no longer the forward force of the car, so why does Newtons First Law Hold true? The only explaination I can think of that the ball in mid air experiences the horizontal motion caused by the cars engine. But what physical expaination can there be for this? Please Register or Log in to view the hidden image!
Hi, Before I start, a bit of friendly advice. Don't start a thread by saying that the laws of physics are wrong. It would be better for you to say that you do not understand Newton's First Law rather than the Law not making sense. No. Newton's First Law says that an object will stay in uniform motion until acted upon by an outside force. This is the same as saying that something will not move until you push it. Agreed? Correct. Because no forces are acting upon it to stop that forward motion. If you threw the ball out the window it would meet air resistance (friction) and would be slowed. Because the force was applied before you threw the ball up. Once in the air nothing is retarding this motion (no force is acting upon it to retard the forward motion), hence it moves along with the car. See above. When the ball is in your pocket it is moving a along with you. You take the ball from your pocket and throw it up in the air. It is still moving along with the car. The only thing that has changed is that you threw it upwards. If you threw that ball forwards it would hit the windshield. Yes? This is becuse you have applied "forward" force to the ball. Now consider this: You throw the ball in the air. Immediately it leaves your hand you jam your foot to the floor on the brake. What happens to the ball? It will hit the windshiled. Why? Because no force was applied to the ball when you hit the brakes in your car. The car slows, but the ball does not. You applied a force to the car, but not the ball. hope that helps Paul aka §lîñk€¥™
OPC51, Welcome to sciforums. First, let me warn you, I'm the official crackpot on these forums. The opinions I express may not be the opinions of the general scientific community. Please Register or Log in to view the hidden image! Now let's get down to the problem. When you accelerate your car, the gravitational field of the ball (and your car) begins to warp. The gravitational field in the front of the ball grows stronger than the gravitational field in the back of the ball. Because of this potential difference in the gravitational field, the ball is more attracted to the space in front of it (by the way, space has a gravitational field) than it is to the space behind it. This results in inertia, or Newton's first law of motion. Now, when you through the ball out of your car, the forward motion continues because the warped gravitational field of the ball is resistant to change (it takes less energy for the gravitational field to remain warped than it does for it to become uniform again). Ok, now I'm in trouble. I'll probably be attacked by every scientist on these forums. Please Register or Log in to view the hidden image! Tom
And rightly so because you are clearly a crackpot. OPC51, I'd advise you to check out Occam's Razor - the simplest answer is usually the correct one. Prosoothus just likes to blind everyone with his ignorance. kind regards Paul aka §lîñk€¥™
§lîñk€¥™, Maybe you'd like to share with all of us your explanation of why an object in a state of motion remains in that state of motion unless acted upon by an external force. I don't recall you explaining this in your previous post. Maybe it's just easier for you to insult people than it is to explain things. Tom
You gave the answer in your question which goes to prove you really are as dumb as I first stated. No, more dumb.
What I mean.. I agree that the forward motion would be uniform (hence no acceleration). I was assuming that the car was a closed system. I was not considering opening windows, changing speed of the car etc. I modelled the situation as a force diagram. Where before it was thrown there was the fores of gravity, normal, friction and car movement on the ball. I then considered the force diagram when the ball is falling. Here I assumed that there was gravity and air resitence. In the before picture there is the horizontal uniform motion motion caused by the car motion. This is transfered to the ball by the act of being connected to the car by being physically held onto. In the second model there is no horizontal force being applied to the ball. It is in no way connected to the car. It is in mid air. No one has ever introduced me to a force that is transmitted via still air (in the closed system) to cause the ball to move horizontally. This is why I entitled my topic as I did. After all I would expect the force diagram that accompanies the before and after model to have same net effect upon horizontal motion. What I am saying is I can no see how the forward motion is maintained in the second model. As a result it would appear that newtons forst law has been voilated. I appreciate that the answer is probably that I am making some basic mistake in my modelling assumptions. What ever it is I would love to know!
OPC51, Imagine that the ball is a battery. As the car accelerates, the ball accelerates because, as you pointed out, it is attached to the car. As the ball accelerates, it gains kinetic energy. This energy is stored in the ball, like electricity (potential difference) is stored in a battery. As the ball is thrown out the window, it retains this kinetic energy, even though it is no longer attached to the car. The ball will hold this energy (and therefore continue to move at the same speed), unless it is acted upon by an outside force. As the ball hits particles of air, some of the kinetic energy is transferred to the air molecules thereby causing the ball to slow down. Tom
Re: What I mean.. How did the ball get into mid air? Teleportation? I am sitting in a moving car with a ball in my hand. I throw the ball upwards. The ball is now moving upwards as well as forwards. I really don't see what you are misunderstanding. kind regards Paul aka §lîñk€¥™
The model My question is this : If we model the situation before and after as I have and you assume that newtons first law hold true. Then the Vector product of the forces in the before and after picture should be the same. I am saying that an analysis of the before model should give the same result as the after model. I.e. they should both have the same horizontal motion. If we look at model 2 there is no horizontal motion. I am asking what mechanism can transfer the necessary motion to the ball in mid air.
The mechanism is in Newtons laws... But nobody knows (well i don`t) What the actual mechanism is. If the universe was a closed system (i assume it is) and it only contained one particle , and `I` gave it a push, how can i know the inertia of the particle? (can i get it from the space/time `field`?) Do i need ANOTHER particle to gauge the movement (force and direction)? Is the ball in the car `related ` to the car and the most distant stars in the universe?
Black Magic? Are we saying this is one of those things we accept because of experimental evidence but can't actually work out how it happen?
newton who??? what is newton or who to be precise???Please Register or Log in to view the hidden image!
Re: newton who??? Isaac Newton was a mathematician/physicist who came up with some of the founding principles of both modern fields. http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Newton.html
REPlease Register or Log in to view the hidden image!PC51 I think that mechanism is the time arrow. If the ball stayed "still" in the air at the place where you threw it up it would have been trawelling back in time.
You toss a ball up in a car. The air inside the car is moving forward at the same rate as the car, thus is not providing a force to push it backward in relation to the car. There the the force you apply upward; the force you apply forward, since you are pushing the ball forward to begin with; and the force of gravity pulling it down. The friction against the air going up and down inside the car is minimal. In comparison, if you toss the ball up outside the car window, the air out there is not moving forward at the same rate as the car; all those particles are much slower, generally. They push the ball backward in relation to the car, so it falls back away.
Why Has No One Said This Yet? (if they have, never mind) Force is dependent upon acceleration, not velocity. F = m * a. There, that feels much better. If you are in a car traveling in a straight line at a constant speed, in Physics Land (no friction), there is no horizontal acceleration and thus no horizontal force acting on the car. The car has a horizontal velocity, but it's not accelerating. Unless there is a horizontal force (*acceleration*) acting on the ball, its horizontal velocity will not change. The reason it is at that velocity is because it was in the car, which (presumably) accelerated in the past in order to acheive that velocity which is now constant. Don't listen to the gravitational fields stuff unless you're in pretty deep; it'll just confuse you.
Despite the objections of people like Prosoothus, the only answer one can give for the question Why does Newton's first law work? is It just does. This is not very fulfilling, but science doesn't concern itself with "explanations." If you model something, and the predictions of your model match reality, then your model is worth something. That is the only criterion for "success." Even Prosoothus' model ignites as many questions as it extinguishes. Let's assume that his model DOES explain inertia (I don't think it does even if one allows oneself to suspend disbelief). He's just replaced the original question with a set of new ones: Why does acceleration warp space? Why does it take less energy for the space to stay warped? ...and maybe a few others, too. So why exactly is your answer useful to anyone, Prosoothus? You'll eventually hit that axiomatic brick wall too, and the only response you'll be able to give is "well, because it just does." - Warren
