Q1: What is the skier's speed at the intermediate point? Using the conservation of momentum, we have the formulas; Wnc = Ef - Eo and Wnc = (1/2mvf2 + mghf) - (1/2mvo2 + mgho) Using the given information, it is stated that the skier starts from rest at the highest point. The initial velocity (Vo) is zero and solving for the final velocity (Vf) we get: VF = [2(Wnc +mg(ho - hf))/m]1/2 Wnc = -400 kJ + 50 kJ = -350 kJ (-350,000 J) m = 60.0 kg, g = 9.8 m/s2, hf Vf = [2({-350 kJ} + {60.0 kg}{9.8m/s2}(3,505 m - 2,901 m))/ {60.0 kg}]1/2 After converting all units to SI, the answer is VF = 12.9 m/s Q2: What is the skier's final velocity (VF) at the foot of the Hart Prairie run? Using the same formulas from the previous equation with a larger Wnc and a lower hf, we end up with 12.8 m/s Q3: Please draw a crude sketch calculating Kinetic energy (KE), Gravitational potential energy (GPE), and total energy at the three points labeled Agassiz (start), Intermediate, and Hart Prairie (final). Use SI (mks) units throughout. Remember: [1.0 m = 3.281 ft] KE = 1/2mv2, GPE = mgh, TE = 1/2mv2+ mgh
Advanced Question: Near the very foot of Hart Prairie run there is a small circular 'speedbump' hill of radius 5.0 m. At what minimum VF will the skier become airborne? Does this particular skier become airborne? (Draw a FBD) Riding this hill involves centripetal force due to the circular shape of it. Knowing that Fnet = ma and Fc = (mv2)/r, we can combine the two to get ma = (mv2)/r. In order to find the necessary velocity to overcome this force we further simplify to; VF= (ar)1/2. Yes, traveling at the skier's current speed of 12.8 m/s the skier will become airborn.
MacIsaac, after Reif F (1995). Understanding Basic Mechanics. Wiley: NY. W180.
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