Here’s a list of some important physics formulas and equations to keep on hand — arranged by topic — so you don’t have to go searching to find them.
Equations of angular motion are relevant wherever you have rotational motions around an axis. When the object has rotated through an angle of θ with an angular velocity of ω and an angular acceleration of α, then you can use these equations to tie these values together.
You must use radians to measure the angle. Also, if you know that the distance from the axis is r, then you can work out the linear distance traveled, s, velocity, v, centripetal acceleration, ac, and force, Fc. When an object with moment of inertia, I (the angular equivalent of mass), has an angular acceleration, α, then there is a net torque Στ.
A heat engine takes heat, Qh, from a high temperature source at temperature Thand moves it to a low temperature sink (temperature Tc) at a rate Qc and, in the process, does mechanical work, W. (This process can be reversed such that work can be performed to move the heat in the opposite direction — a heat pump.) The amount of work performed in proportion to the amount of heat extracted from the heat source is the efficiency of the engine. A Carnot engine is reversible and has the maximum possible efficiency, given by the following equations. The equivalent of efficiency for a heat pump is the coefficient of performance.
A volume, V, of fluid with mass, m, has density, ρ. A force, F, over an area, A, gives rise to a pressure, P. The pressure of a fluid at a depth of h depends on the density and the gravitational constant, g. Objects immersed in a fluid causing a mass of weight, Wwater displaced, give rise to an upward directed buoyancy force, Fbuoyancy. Because of the conservation of mass, the volume flow rate of a fluid moving with velocity, v, through a cross-sectional area, A, is constant. Bernoulli’s equation relates the pressure and speed of a fluid.
A mass, m, accelerates at a rate, a, due to a force, F, acting. Frictional forces, FF, are in proportion to the normal force between the materials, FN, with a coefficient of friction, μ. Two masses, m1 and m2, separated by a distance, r,attract each other with a gravitational force, given by the following equations, in proportion to the gravitational constant G:
MOMENTS OF INERTIA
The rotational equivalent of mass is inertia, I, which depends on how an object’s mass is distributed through space. The moments of inertia for various shapes are shown here:
Disk rotating around its center:
Hollow cylinder rotating around its center: I = mr2
Hollow sphere rotating an axis through its center:
Hoop rotating around its center: I = mr2
Point mass rotating at radius r: I = mr2
Rectangle rotating around an axis along one edge where the other edge is of length r:
Rectangle rotating around an axis parallel to one edge and passing through the center, where the length of the other edge is r:
Rod rotating around an axis perpendicular to it and through its center:
Rod rotating around an axis perpendicular to it and through one end:
Solid cylinder, rotating around an axis along its center line:
The kinetic energy of a rotating body, with moment of inertia, I, and angular velocity, ω:
The angular momentum of a rotating body with moment of inertia, I, and angular velocity, ω:
When an object at position x moves with velocity, v, and acceleration, a, resulting in displacement, s, each of these components is related by the following equations: