Physics

The device used to change the speed of an electric fan is regulator.

The potential energy of a body when raised through height h is given by mgh. Each time, a normal rubber ball hits the floor, it loses one-fifth of its total energy and the rebound height is proportional to energy, so each bounce will rebound to four-fifth of the previous bounce. But, the question states that there is no loss of energy/velocity after rebounding. So the height of 2 metres will be maintained.

The Moon does not rotate. The Moon does spin on its axis, completing a rotation once every 27.3 days; the confusion is caused because it also takes the same period to orbit the Earth, so that it keeps the same side facing us.

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. Reduce the friction as rolling friction is the least, rather than sliding or static friction.

L = inductance is proportional to the number of turns per unit length. So self inductance becomes three times. if turns in a coil is trippled, self inductance become nine times.

The word “Physics” comes from the Greek word Fusis.

Diffraction is the slight bending of light as it passes around the edge of an object. The amount of bending depends on the relative size of the wavelength of light to the size of the opening.

A lens is a transmissive optical device that focuses or disperses a light beam by the process of refraction._x000D_ Flint glass is used as an optical glass because it has relatively high refractive index and low Abbe number than other materials.

Here oil is the most viscous liquid.