Term

Definition
Momentum = mass x velocity Units are kgms^{1} or Ns Momentum is a vector quantity, direction is very important. 


Term
State the principle of conservation of momentum 

Definition
If there are no external forces involved in a collision then momentum is conserved, Total momentum before = Toal momentum after 


Term
What is an elastic collision? 

Definition
In an elastic collision both momentum and kinetic energy are conserved. Momentum before = Momentum after E_{k} before = E_{k} after 


Term
What is an inelastic collision? 

Definition
In a collision but kinetic energy is not conserved. 


Term
What causes a change in momentum? What is the equation for change in momentum? 

Definition
A resultant force acting on an object will change its momentum. The longer the force acts on an object, the greater the change in momentum. Change in momentum = resultant force x time 


Term
How can force be defined in terms of momentum? What and how is this related to Newton's 2nd law? 

Definition
Resultant force = change in momentum/time taken Newton's 2nd law states that the rate of change of momentum is proportional to the resultant force that produces it. Rate of change of momentum = change in momentum / time taken = resultant force F = Δp/t = (Δmv)/t = m(Δv/t) = ma 


Term

Definition
When two bodies interact, the they exert on each other are equal and opposite. It can also be written as, Forces work in pairs. Every action produces an equal but opposite reaction. 

