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Physics - Newtonian
Physics - Newtonian world
|Newton’s first law
|One of Newton’s three laws of motion. An object will remain at rest or continue travelling at a constant velocity unless acted upon by a force.
|Newton’s second law
|One of Newton’s three laws of motion. The rate of change of the momentum of an object is directly proportional to the resultant force acting upon it and the change in the momentum is in the same direction as the force. Often written as F = Δp/Δt.
|Newton’s third law
|One of Newton’s three laws of motion. When body A exerts a force on body B, body B exerts an equal and opposite force on body A.
|linear momentum (p)
|The product of an object’s mass and velocity, given by p = mv. Measured in kg ms–1; a vector quantity.
|The product of the force acting on a body and the time it is acting, given by impulse = FΔt. It can also be considered to be the change in momentum of a body. Measured in N s or kg m s–1.
|conservation of momentum
|Physical law stating that in the absence of external forces the total momentum of a system remains constant.
|elastic collision (perfectly)
|In a perfectly elastic collision kinetic energy and momentum are conserved.
|Force per unit area, measured in pascals (Pa), e.g. 100 000 Pa. 1 Pa = 1 Nm–1. A scalar quantity.
|A collision where momentum is conserved but kinetic energy is not.
|Unit of angle or phase difference (rad), e.g. 3π rad. One radian is the angle subtended at the center of a circle by an arc of circumference that is equal in length to the radius of the circle. 2π = 360o.
|centripetal acceleration (a)
|The acceleration of a body moving in a circle with constant speed acting towards the centre of the circle. Given by a = v^2/r, measured in ms–2.
|gravitational field strength (g)
|The gravitational field strength at any point is the force acting per unit mass at that point. Measured in N kg–1. On the surface of the Earth g = 9.81 N kg–1.
|Newton’s law of gravitation
|The gravitational force of attraction between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres of mass.
|Kepler’s third law
|The period of a planet orbiting the sun squared is proportional to the mean radius of its orbit cubed. T^2 proportional to r^3.
|An orbit of the Earth made by a satellite that has the same time period as the rotation of the Earth (i.e. 24 hours) and is in the equatorial plane.
|simple harmonic motion (SHM)
|When the acceleration a of an object is proportional to its displacement x and the acceleration is in the opposite direction to the displacement. a proportional to –x.
|The displacement of a body undergoing SHM from the rest or equilibrium position. Given by x = xo sin (2πft) or x= xo sin (2πft). Measured in metres (m).
|amplitude, oscillations (xo)
|The maximum displacement from the rest or equilibrium position, measured in metres (m).
|The time taken for one complete pattern of oscillation, measured in seconds (s).
|phase difference, oscillations (Φ)
|A measure of the relationship between the pattern of vibration at two points. Two points that have the same pattern of vibration are in phase. Two points that have exactly the opposite pattern of vibration are out of phase. (rad).
|The number of oscillations per unit time, measured in hertz (Hz), e.g. 50 Hz.
|Angular frequency 2Pif
|omega. 2Pif per unit time. The number of complete cycles per unit time.
|When the driving frequency is equal to the natural frequency of an oscillating system. This causes a dramatic increase in the amplitude of the oscillations.
|The sum of all the kinetic and potential energies of molecules within a substance.
|specific heat capacity
|The energy required to raise the temperature of 1 kg of a substance by 1 K. Measured in J kg–1 K–1.
|specific latent heat of fusion
|The energy required to change the state of 1 kg of a substance at its melting point from solid to liquid. Measured in J kg–1.
|specific latent heat of vaporisation
|The energy required to change the state of 1 kg of a substance at its boiling point from liquid to gas. Measured in J kg–1.
|The volume of a fixed mass of gas is inversely proportional to pressure exerted on it, provided temperature remains constant
|The condition whereby two objects are at the same temperature and so there is no net thermal energy transfer between them.