A radioactive substance has a half-life of 3 minutes. After 9 minutes, the count rate was observed to be 200. What was the count rate at zero time?

The half-life of a radioactive substance is 2 seconds. Calculate the decay constant.

A particle of charge q and mass m moving with a velocity v enters a uniform magnetic field B in the direction of the field. The force on the particle is

When electrical power is transmitted over long distances, the voltage is stepped up so that

A gas occupies a certain volume at 27°C. At what temperature will its volume be twice times the original volume assuming that its pressure remains constant?

The helium isotope \(^3_2He\)

Which of the following is used in a nuclear reactor to slow down fast moving neutrons?

When a metal is heated to a high temperature, electrons are emitted from its surface. The process is known as

A piece of stone weights 180 N in air and 150 N in a beaker containing 160 N of methylated spirit. What is the up thrust exerted on the stone?