# Shared Flashcard Set

## Details

OCR A Forces,Fields and Energy
Collisions and momentum
7
Physics
04/28/2008

Term
 Define linear momentum
Definition
 Momentum = mass x velocityUnits are kgms-1 or NsMomentum 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 afterEk before = Ek 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 forceF = Δp/t = (Δmv)/t = m(Δv/t) = ma
Term
 Define Newton's 3rd law
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.
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