Name the radioactive radiations which have the least penetrating power. 

A boy weighs 360 N on Earth.

i) What would be his approximate weight on the moon?

A body is acted upon by a force. State two conditions under which the work done could be zero. 

A spring is kept compressed by a small trolley of mass 0.5 kg lying on a smooth horizontal surface as shown in the figure:

i) Define the term momentum.

ii) How is force related to the momentum of a body?

iii) State the condition when the change in momentum of a body depends only on the change in its velocity. 

A body of mass 50 kg has a momentum 3000 kg m/s. Calculate:

i) the kinetic energy of the body.

ii) the velocity of the body. 

i) Why is the mechanical advantage of a lever of the second order always greater than one?

i) What is meant by refraction of light?

ii) What is the cause of refraction of light? 

9.

The refractive index of diamond is 2.42. What is meant by this statement? 

A stick partly immersed in water appears to be bent. Draw a ray diagram to show the bending of the stick. When placed in water and viewed obliquely from above.