Quote:
Originally Posted by cr45
You appear to be confusing the term "inertia" with "kinetic energy".
A mass M moving at a velocity V has a kinetic energy of 0.5 * M * V * V.
This however is not inertia.
Inertia is a measure of a body's resistance to changes in velocity.
It can be found from Newton's second law F = M * A and thus M = F / A
As there is no gravity in space, astronauts determine their mass (inertia) in a special device that applies a force and the rate of acceleration is measured. The rearranged Newtons 2nd equation is then used to calculate their mass (inertia).
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You are right. Inertia is mass (resistance to change speed), and rotational inertia is resistance to change rotational motion.
A bigger wheel has way bigger rotational inertia, but it covers a much larger distance than a smaller wheel rotating bat the same speed.
In the end what matters is how fast the thread moves - that's the same as the speed of the car, regardless of the size of the wheels.
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