Physics Lect 4

 Momentum p = mvin an isolated system momentum is always conserveda vector Collisions are either: 1) Elastic - mechanical energy is conserved, all E is transferred between objects2) Inelastic - momentum is conserved, some E is transferred to internal E Completely Inelastic Collisions Stick together and pi = pf Solving Inelastic Collisions draw 2 systems: 1 right before the collision and one right after Reverse Collisions Start from rest and then burst apartpi = pf = 0in order to conserve momentum they must sep. in exactly opp. directionsineslastic What is nec. in order for an object to "bounce back" after it has struck another object? It must have less mass than the object it has hit Impulse Change in MomentumJ = Δp = Δmv or J = Fave Δt this states that if the time over which a force acts is increased, the same Δv can be achieved (how airbags reduce force on a passenger) Machines Reduce the amount of F needed to do work but does not change the amount of WRamp, Lever, Pulley: all F proportional to 1 / d Radioactive Decay All atoms undergo decay except H1:1 prot:neut ratios help to stablize smaller atoms Alpha Decay 42 aemittedR side of arrow Authorlaskiru ID58879 Card SetPhysics Lect 4 DescriptionMomentum, Machines, Radio Active Decay Updated2011-01-10T03:25:01Z Show Answers