What are the seven basic physical quantities? answer Temperature (K) Length (m) Luminous intensity (Cd) Mass (kg) Number of particles (moles) Time (s) Charge (C)

What is meant by the "half-life" of a radioactive substance? answer Half-life is the time taken for half the number of a specific type of radioactive nuclei to decay. It is constant. dN/dt = -kN therefore by integration, N = Noe^(-kt) lnN = lnNo - kt lnNo - lnN = kt Now, when N = No/2, ln2 = kt½ thus t½ = ln2/k where k is the decay constant, N is the number or mass of radioactive nuclei at time t, No is N at t=0.

What is a Tesla? answer A Tesla (T) is a unit of magnetic field strength. It is the magnetic field strength required to produce a force of 1 N on a charge of 1 coulomb travelling 1 m/s perpendicularly to the magntic field.

What are some useful equations concerning uniformly accelerating bodies? answer 1. v = u + at 2. v² = u² + 2as 3. s = ut + ½ at²