Maybe I'm a little late for this, but in the interest of not wasting the ~10 minutes I spent typing this up:
esvion said:
I am a chemistry student and don't know much about physics. I am trying to understand the definition of the coulomb. Correct me if I am wrong please...
A Newton is the amount of work it takes to push one kilogram 1 meter per second... Two Newtons would accelerate the object from 0 m/s to 2 m/s..
As the previous replies have pointed out, a Newton is a certain amount of
force (not work). Force in physics is the thing you apply to an object to increase its velocity. (Actually to increase its momentum, but that's another story) One Newton of force will push a kilogram 1 meter per second
faster than it was going before
for every second the force is applied. If you push on a 1-kilogram mass with a force of 1 Newton for 1 second, it will be going 1 m/s faster. If you push on 1 kg with 1 N for 2 seconds, it will be going 2 m/s faster. Or if you push on 1 kg with 2 N for 1 second, it will also be going 2 m/s faster. The stronger the force, the more the velocity increases; but also, the longer you apply the force, the more the velocity increases. The equation for this is
F \Delta t = m \Delta v
You can see that the change in velocity \Delta v is proportional to the force, but also to the change in time. Incidentally, if you rearrange that a little you get
F = m \frac{\Delta v}{\Delta t}
But \Delta v/\Delta t is just the rate of change in velocity, a.k.a. the acceleration
a. So
F =
ma - guess what, you just derived Newton's second law of motion :-)
esvion said:
Would an object traveling at 5 m/s require an additional 1 N to accelerate it to 6 m/s? I thought it would require more and more energy (or Newtons) to push an already moving object even faster - more than just 1 N. I can't quite understand the difference between a joule and a Newton. I can see how the mass is square in the formula for a joule, but can't understand why. Can anyone help me with this?
Again, as the previous answers have pointed out, an object traveling at 5 m/s would only require 1 N (
for 1 second) to accelerate it to 6 m/s. It takes the same amount of force, for the same amount of time, to change the velocity by 1 m/s, regardless of whether the object is moving already or not. However, it does take more and more
energy (which is measured in Joules) to accelerate something the faster it moves. Energy is something the object has, whereas force is something you apply to the object. Think about it this way: when you push on something, you can feel the force you're applying to it (actually you feel the force it's applying to you, but again, that's another story). But how much energy it takes depends on whether the thing is moving or not, and how fast. You could lean against a solid wall all day and not even get tired - in that case, you can feel that there's a force, but you're not losing any energy because you're not moving. On the other hand, if you go for a jog you're basically pushing yourself along the ground; you might be applying the same force that you did to the wall, but it makes you pretty tired because now you have to get yourself moving. And once you get moving, it becomes increasingly more tiring to run faster and faster.
The mathematical reason it takes more energy, but not more force, to accelerate something that's already moving faster, lies in the formula
E = \frac{1}{2}mv^2
E is the energy and
v is the velocity. If a 1-kilogram mass is moving at 1 m/s, it has an energy of 1 Joule. If it's moving at 2 m/s, it has 4 Joules; 3 m/s gives it 9 Joules, and so on (4 ->16, 5 ->25). So to accelerate it from 4 m/s to 5 m/s takes 9 Joules, whereas to accelerate it from 1 m/s to 2 m/s only takes 3 Joules. At higher speeds, it takes more energy to apply the same amount of force.
