Physics laws and formulae (O level)
This list is a list of physics laws and formulae used in O level physics.
Equations of motion with constant acceleration
Hooke’s law – that the extension was of a material is proportional to the stretching force provided the material is not permanently stretched.
Parallelogram law – If two forces acting at a point are represented in size and direction by the sides of a parallelogram, their resultant is represented in size and direction by the diagonal of the parallelogram drawn at that point.
Newton’s first law of motion – A body stays in its state of rest or uniform velocity unless acted upon by an external force.
Newton’s second law of motion – The acceleration of a body is directly proportional to the resultant force acting on it.
Newton’s third law of motion – To every action there is an equal and opposite reaction.
Law of moments – When a body is in equilibrium the sum of the clockwise moments about any point is equal to the sum of the anticlockwise moments about the same point.
moment of a force = force × perpendicular distance of the line of action of the force from the pivot
Work, energy and power
Law of conservation of energy – energy can neither be created nor destroyed but can be converted from one form to another.
Boyle’s law – The pressure of a fixed mass of gas is inversely proportional to its volume if its temperature is kept constant.
Charles’s law – The volume of a fixed mass of gas is directly proportional to its absolute temperature if the pressure is kept constant.
Pressure law – The pressure of a fixed mass of gas is directly proportional to its absolute temperature if the volume is kept constant.
Waves and optics
Law of reflection – The angle of incidence is equal to the angle of reflection.
- Law of magnetic attraction – Like poles repel, unlike poles attract.
Law of electrostatic attraction – Like charges repel, unlike charges attract.
Ohm’s law – The current in an ohmic conductor is directly proportional to the p.d. across its ends if the temperature is kept constant.
Resistors in series
Resistors in parallel
Faraday’s law – The size of the induced p.d. is directly proportional to the rate at which the conductor cuts magnetic field lines.
Lenz law – The direction of the induced current is such as to oppose the change causing it.