Which physical quantity does this electronvolt measure? How is it related to the S.I. unit of this quantity?

What should be the angle between force and displacement be to get the

i) minimum work

State Newton’s Second Law of motion. 

The work done by the heart is 1 Joule per beat. Calculate the power of the heart if it beats 72 times in one minute. 

Mention two properties of a wave: one property which varies and the other which remains constant when the wave passes from one medium to another.

Explain briefly what causes the twinkling of stars at night? 

State two advantages of an aneroid barometer. 

Explain why a gas bubble released at the bottom of a lake grows in size as it rises to the surface of the lake? 

What is meant by the statement, ‘ the critical angle for diamond is 24^o? How is the critical angle of a material related to its refractive index?  

10.

A block of wood of volume 25 cm³ floats in water with 20 cm³ of its volume immersed. Calculate:

i) the density, and

ii) the weight of the block of wood.