Q&A for How to Derive the Formula for Kinetic Energy

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How do I calculate kinetic energy using the equations of motion?

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K=1/2mv^2. You can take any equation of motion, solve for v and then substitute in the equation above. I could provide more help if you gave the specific equation.

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How do I calculate potential and kinetic energy involving projectile of a ball without given mass?

Community Answer

You can not, since energy is a function of both mass and velocity. If you know the velocity but not the mass, you can turn it into a function of mass, since velocity becomes a constant; you could have K = 7m, where m is the mass. Just be sure to mind your units.

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Question

Why are we using the timeless equation?

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We're using the timeless equation because we know that the kinetic energy of something shouldn't depend on time. So by using this equation, we can arrive at the answer in the simplest possible way. Otherwise, we would have to find a way to cancel the time variable that would be introduced.

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How do I calculate the unit of escape velocity in miles per second?

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From the surface of the Earth, escape velocity (ignoring air friction) is about 7 miles per second, or 25,000 miles per hour. Given that initial speed, an object needs no additional force applied to completely escape Earth's gravity.

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Question

How would this derivation look like if the mass is not constant?

Community Answer

This is a concept of limit. Mass can never be constant, but the change is very negligible, hence it tends not to change. It would have been impossible to calculate if mass would have not been constant. It will now depend on the time the mass is being calculated, because it is not constant.

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