PHY 101 1nd Edition Lecture 16 Outline of Last Lecture I. Work – Energy Theorem Revisited Cont.II. 5.6 PowerIII. Chapter 6: Momentum & CollisionsIV. 6.1 Momentum & Impulsea. Impulse – Momentum Theoremb. Varying ForceOutline of Current Lecture V. Comparison: Impulse – Momentum Theorem vs. Work – Energy TheoremVI. Relationship Between Kinetic Energy & MomentumCurrent LectureComparison: Impulse – Momentum Theorem vs. Work – Energy Theorem- Work – energy theoremo W = F; Δx = ΔKEo ΔKE = KEf – KEio KE = ½mv2o Unit of energy, work: kg·m2/s2 = N·mo Work: distance total- Impulse – Momentum Theoremo I = FΔt = Δpo Δp = pf – pio P = mvo Unit of momentum, impulse: Kg·m/s = N·so Impulse: time total- Example: Force on a golf ballo A golf ball of mass 5 x 10-2kg is struck by a club. The ball leaves with a speed v = 40m/so If the duration of contact time (collision time) is 8 x 10-4s, find the average force acting on the golf ballo Solution: the change in golf ball’s momentumo Δp = mvf – mvi = mvfo Δp = 5 x 10-2 x 40 = 2 kg·m/sThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Apply the impulse – momentum theorem Fav Δt = Δpo Fav = Δp/Δt = 2/8 x10-4 = 2 x 103N = 560 lb- Example: Crash Testo A car of mass 1.5 x 102 kg hits the wall with an initial velocity of -15m/s. the car rebounds with a final velocity of 2.6m/s. the collision time is 0.15s.o 1) calculate the impulse delivered to the caro 2) average force exerted on the car during the collision Solution: the change in the car’s momentum Δp = mvf – mvi I = favΔt = Δp Δp = 1.5 x 103 x 2.6 – 1.5 x 103 x (-15) = 2.64 x 104 kg·m/s Therefore, I = Δp = 2.64 x 104 kg·m/so The average force exerted on the car during the collision F = Δp/Δt = 2.64 x 104/0.15 = 1.76 x 105N = 39,600 lbRelationship Between Kinetic Energy and Momentum- Momentum p = mv, a vector quantity- Magnitude of momentum: p = mv, a scalar quantity- Kinetic Energy (Scalar)o KE = 1/2mv2 = m2v2/2m =
View Full Document
Unlocking...