Explain the principle behind the wind up toys.

SUPPOSINGLY THERE IS LIFE ON EARTH AND MOON WHERE WILL ONE BUY GOLD FROM AND SELL WHERE ? AND WHY ? 

A glass full of water has a bottom of area 20 cm² , top of area 20 cm² , height 20 cm and volume half a litre.

(a) Find the force exerted by the water on  the bottom

(b) Considering the equilibrium of the water, find the resultant force exerted by the sides of the glass on the warer.

Atmospheric pressure = 1.0 * 10⁵ N m^-2 Density of water = 1000 kg m^-3 and g = 10 m s^-2. .Take all numbers to be exact

A cubical block of ice floating in water has to support a metal piece weighing 0.5 kg. what can be the minimum edge of the block so that it does not sink in water? Specific gravity of ice is 0.9

a cubical box is to be constructed with iron sheets 1 mm in thickness. What can be the minimum value of the external edge so that the cube does not sink in water ? density of iron = 8000 kg m^-3 and density of water = 1000 kg m^-3

An ornament weighing 36 g in air, weighs only 34 g in water. Assuming that some copper is mixed with gold to prepare the ornament, find the amount of copper in it. Specific gravity of gold is 19.3 and that of copper is 8.9

Referring to this problem, suppose, the goldsmith argues that he has not mixed copper or any other material with gold, rather some cavities might have been left inside the ornament. Calculate the volume of the cavities left that will allow the weights given in that problem.