Problem 11. Sand
Dry sand is rather ‘soft' to walk on when compared to damp sand. However sand containing a significant amount of water becomes soft again. Investigate the parameters that affect the softness of sand.
Problem 12. Wet towels
When a wet towel is flicked, it may create a cracking sound like a whip. Investigate the effect. Why does a wet towel crack louder than a dry one?
Problem 13. Shrieking rod
A metal rod is held between two fingers and hit. Investigate how the sound produced depends on the position of holding and hitting the rod?
Problem 14. Magnetic spring
Two magnets are arranged on top of each other such that one of them is fixed and the other one can move vertically. Investigate oscillations of the magnet.
Probelm 15. Paper anemometer
When thin strips of paper are placed in an air flow, a noise may be heard. Investigate how the velocity of the air flow can be deduced from this noise?
Problem 16. Rotating spring
A helical spring is rotated about one of its ends around a vertical axis. Investigate the expansion of the spring with and without an additional mass attached to its free end.
Problem 17. Kelvin's dropper
Construct Kelvin's dropper. Measure the highest voltage it can produce. Investigate its dependence on relevant parameters.