When does a convex lens act like a magnifying glass

In raising a 6200-n piano with a pulley system, the movers note that, for every 2.2 m of rope pulled down, the piano rises 0.12 m . ideally, find the force required to lift the piano.

If the speed of a particle triples ,by what factor does its kinetic energy increase?

Explain earth's motion, using the terms "precession" and "rotation" in your answer.