advertisement

Keywords and Equations Make sure you know the definition of all of these key words, phrases and equations from the forces topic and any units. If they are formulae make sure you know and can rearrange them to use them. Keyword Definition Units Average speed Speed over a journey over a particular distance and time (Can have variations of instantaneous speeds within it) Speed at a particular moment in time m/s Instantaneous speed Speed equation Positive distance Negative distance Velocity Stationary Interaction Pair Reaction Up-thrust Friction Weight equation Momentum Equation Change in Momentum Equation Resultant force Counter force Kinetic energy Gravitational Potential energy Work done Equation Speed = distance / time (m/s) (m) (s) Distance away from a starting point Distance in opposite direction to positive distance Speed in a particular direction When an object is at rest Two forces that are equal and size and opposite in direction. Both forces act on different objects Upward force produced by a surface when an object is placed on it Upward force produced by water when an object floats on it Force that acts in the opposite direction to movement Weight = mass x gravity (N) (kg) (N/kg) Momentum = mass x velocity (kg m/s) (kg) (m/s) Change in momentum = force x time force acts (kg m/s) (N) (s) Sum of all individual forces acting on an object taking into account their direction Force that acts in opposite direction to another Energy possessed by a moving object Energy that is stored in an object that will fall due to gravity Work done = force x distance (J) (N) (m) m/s m m m/s N N N J J Conservation of Energy GPE equation KE equation Assuming that there in no friction and no air resistance on a falling object Loss in GPE = Gain in KE GPE = weight x height (J) (N) (m) KE = ½ x mass x (speed)2 (J) (kg) (m/s)