Forces

Weight (W) Weight is a force due to the mass of an object and a gravitational field. It is given by the formula: W = mg (g = 9.81 ms^-2 is different from 9.81 Nkg^-1)	Electrostatic Force (Fe) This force acts between two charges + and -	Friction (F or D) Friction acts between surfaces. It always acts in the opposite direction to the velocity
Upthrust (U) Upthrust acts on objects in fluid and is responsible for making objects float	Drag (D) And Air Resistance Air resistance acts on an object as it moves through the air. It is a friction between the object and the air particles. Air resistance can also be called Drag. Drag can also act between an object and liquid. These always act in the opposite direction to the velocity	Thrust or Motive Force (T) Thrust is a force from an engine, rocket or anything which drives the object fowards
Normal Reaction (R) Normal reaction is a push force between surfaces. It always acts normally (i.e at right angle to the surface)	Tension (T) Tension is the force in a string or a spring: T=kx (k is spring constant and x is extension)	Gravitational Force Gravitational force keeps moon in orbit (in A2 not AS)
Lift (L) This is a force used to keep an object in the air	Magnetic Force (Fm or Fb) Magnetic forces act between magnets or moving charges

BVIS HANOI (VV)