Fill in the blanks in the following sentences with appropriate words: 

During the emission of a beta particle, the ____ number remains the same. 

Fill in the blanks in the following sentences with appropriate words: 

The minimum amount of energy required to emit an electron from a metal surface is called ____. 

Define one Newton.

Where does the position of centre of gravity for,

i) a circle lamina

ii) a triangular lamina?

A coolie carrying a load on his head and moving on a frictionless horizontal platform does no work. Explain the reason why? 

A uniform metre scale can be balanced at the 70.0 cm mark when a mass of 0.05 kg is hung from the 94.0 cm mark.

i) Draw a diagram of the arrangement.

ii) Find the mass of the metre scale.

A man can open a nut by applying a force of 150 N by using a lever handle of length 0.4 m. What should be the length of the handle if he is able to open it by applying a force of 60 N.

A ball of mass 200 g falls from a height of 5m. What will be its kinetic energy when it just reaches the ground? 

Draw a diagram to show the energy changes in an oscillating simple pendulum. Indicate in your diagram how the total mechanical energy in it remains constant during the oscillation? 

Name a machine which can be used to,

i) multiply forces

ii) change the direction of the force applied