An object is attached to the lower end of a 100-coil spring that is hanging from the ceiling. The spring stretches by 0.160 m. The spring is then cut into 2 identical springs of 50 coils each. Each spring is attached between the ceiling and the object. By how much does each spring stretch?
A piano wire (Y=2.0*10^10 N/m^2) has a radius of 0.80 mm and a length of 0.76 m. One end of the wire is wrapped around a tuning peg whose radius is 1.8 mm. The other end is fixed in place. Initially, there is no tension in the wire. Find the tension when the peg is turned through 2 revolutions.
Suppose you were kidnapped and held prisoner by space invaders in a completely isolated room, with nothing but a watch and a pair of shoes (including shoelaces of known length). Explain how you might determine whether this room is on Earth or on the moon.