Momentum & energy

Momentum P = mv Momentum is mass in motion Vector quantity Dimensions?

Force & Momentum Force is the derivative of momentum as a function of time. F = ∆P/∆t = m∆v/∆t Of course ∆v/∆t is accel.

Momentum Conservation The momentum of a system is always conserved. Complication - P is a vector qty. - which means we will have vector considerations when working w/ P conservation. P o = P f Like relative velocity we have to create the exact formula based on the specific circumstance.

Scenarios for P conservation Explosion P o = P 1 + P 2 +…. + P n ; exact formula depends on # of pcs. before & after. Collisions --> Explosion P 1o + P 2o = P 1f + P 2f ; exact formula depends on # of pcs. before & after Collision --> Coalescence P 1o + P 2o = P f ; typically here only 2 pcs. collide, see problem #13, p.238

Energy Exist in 7 forms - crimsen --> cr(h)msen Can be transferred - always involves same form of energy. Can be transformed - involves more than 1 form. Scalar quantity Energy is defined as the ability to do work. Discuss implications.

Mechanical Energy 2 forms 1) kinetic, 2) potential E k = 1/2mv 2 E p = mgh

Work W = Fd W = ∆E k W = ∆E p Work like E is a scalar quantity?? Fig. 10-2, p. 258

Energy Conservation The energy of a system is always conserved. Complication - 7 forms of energy & 2 forms of mech. E. Elastic collision - mech. E conserved Inelastic collision - mech. E is not conserved. Falling body - E po = E kf Exact form of E conservation eq. Is circumstance dependent.

P & E conservation Occurring to every the same time. Complicated b/c P is vector & E is scalar & b/c energy exist in 7 forms.