Force, Work, Energy and Power — Physics STD 10 — Question

What do you mean by latent heat?

The efficiency of a pulley is always less than 100%.

The nucleus of an atom does not contain electrons. Explain how is it possible for the nucleus to emit a beta particle which is fast moving electron.

Which scale of temperature is commonly used and why?

A bucket contains 10 liters of water at 80°C. Cold water at 25°C is run from a tap into the bucket of hot water for 20 seconds and the temp. Of the water in the bucket falls to 50°C.
(a) Calculate the rate at which cold water came out of the tap.
(b) State an assumption made in the above calculation.

State two ways by which the speed of rotation of an electric motor can be increased?

Define 'joule'.

After a robbery, if a window has been broken, there will be tiny particles of glass. Some of these will be found at the scene of the crime and some may be caught in the thief’s clothing. If the police can prove that these particles are identical, they have a strong case.
A method of doing this is to suspend the particles of glass in a special liquid. Light of a single colour is thrown through the liquid and the particles viewed through a microscope. The temperature of the liquid is then slowly altered. This alters the speed of light through the liquid (i.e., it alters the refractive index). At one particular temperature, the particles of glass disappear. It this happens at the same temperature for both sets of glass particles, they probably came from the same broken pane of glass.
Complete and copy the diagram to show how light bends when it travels from the liquid to the glass and back to the liquid, If the light slows down in the glass.