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_Enigma_
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OK. I have a problem. I've just started taking physics (1 month) so for more experienced physicists this should be simple.
The kinetic energy of an object is: KE = 1/2*m*v^2
Right?
This means that a spaceship would use a lot more energy to accelerate from 100m/s to 105m/s than it would do by accelerating from 0m/s to 5m/s.
But this is contrary to what my intuition tells me. My intuition tells me that it uses the same amount of energy in both cases. Am I wrong?
Some examples that support my idea:
Please help me! What is wrong? Oh, and I'm not very good at maths (2nd year high school) so try to make the explanation simpel.
thx
The kinetic energy of an object is: KE = 1/2*m*v^2
Right?
This means that a spaceship would use a lot more energy to accelerate from 100m/s to 105m/s than it would do by accelerating from 0m/s to 5m/s.
But this is contrary to what my intuition tells me. My intuition tells me that it uses the same amount of energy in both cases. Am I wrong?
Some examples that support my idea:
According to general relativity, everybody has equal right to claim that they are standing still, and that everything else is moving.
So, let's say that space shuttle A is standing still. Right next to it is space shuttle B which is also standing still. On the opposite side of Space shuttle B, is space C. Space shuttle C is traveling at 100m/s. Then space shuttle B accelerates to 5m/s in the opposite direction of the motion of space shuttle C using a certain amount of energy.
Now to space shuttle A it's obvious that the energy space shuttle B used is:
1/2*m*5^2 - 1/2*m*0^2 = 12.5*m
But to space shuttle C, which can claim that it's standing still and that Space shuttle A is traveling at 100m/s, whereas Space shuttle B was traveling at 100m/s alongside A, but is now traveling at 105m/s it seems that the energy used to accelerate space shuttle B was:
1/2*m*105^2 - 1/2*m*100^2 = 512.5*m, which is a lot more than what space shuttle A thinks that space shuttle B used.
Obviously there is something wrong here. I mean, space shuttle B used only a one amount of energy. So what's wrong?
A man standing still on a train traveling at 100m/s accelerates from 0m/s to 5m/s. To do this he used a small amount of energy. But to a person standing still outside the train it seems that he used a lot more energy just like in the example above
An object falling freely (neglecting air resistance) will accelerate at a constant rate. But the force exerted on it by gravity is also constant. This doesn't fit with KE = 1/2*m*v^2
Please help me! What is wrong? Oh, and I'm not very good at maths (2nd year high school) so try to make the explanation simpel.
thx