The activity of a sample of caesium-137 is initially 40 kBq. How long will it take for the activity of the sample to fall by 30 kBq? (The half-life of caesium is approximately 30 years.)

Aparticle moves according to a law of motion s = f(t), 0 ≤ t ≤ 12, where t is measured in seconds and s in feet. f(t) = cos(πt/6) (a) find the velocity at time t (in ft/s).

While standing outdoors one evening, you are exposed to the following four types of electromagnetic radiation: yellow light from a sodium street lamp, radio waves from an am radio station, radio waves from an fm radio station, and microwaves from an antenna of a communications system. rank these type of waves in terms of increasing photon energy.

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?