Which of the following pairs is part of the electromagnetic spectrum? 

I. Radio waves

II. sound waves

III. Gamma rays

IV. water waves

A substance has half of 3 min. After 6 min, the count rate was observed to be 400. What was its count rate at zero time? 

The slope of the straight line displacement-time graph indicates?

A man will exert the greatest pressure when he?

Which of the units of the following physical quantities are derived?

I. Area
II. Thrust
III. Pressure
IV. Mass