Explain James Dewar hydrogen experiment and how it applied to absolute zero.

Wo audio speakers are placed on a vertical rail. speaker a is placed at head-level while speaker b is place at some variable height, \delta yδy, above speaker a. both speakers receive simultaneous input from a sine-wave generator so the speakers each produce a pure sinusoidal sound wave with a wavelength of 0.531 meters. calculate the lowest height that speaker b can be placed above speaker a to produce a minimum of sound heard by person standing \delta x = 7.86δx=7.86 meters directly in front of speaker a.

If steel is more dense that lake water, why can a boat float

If a tank filled with water contains a block and the height of the water above point a within the block is 0.8 meter, what is the pressure at point a?