The masses of the javelin, discus, and shot are 0.80 kg, 2.0 kg, and 7.2 kg, res
ID: 1973077 • Letter: T
Question
The masses of the javelin, discus, and shot are 0.80 kg, 2.0 kg, and 7.2 kg, respectively, and record throws in the corresponding track events are about 89 m, 69 m, and 21 m, respectively.(a) Neglecting air resistance, calculate the minimum initial kinetic energies that would produce these throws.
javelin J
discus J
shot J
(b) Neglecting air resistance, estimate the average force exerted on each object during the throw, assuming the force acts over a distance of 2.0 m.
javelin N
discus N
shot N
(c) Do your results suggest that air resistance is an important factor?
Explanation / Answer
The idea is to first use the range equation for eachobject: max range = v2 /g to find v2 foreach . javelin: v2 = 9.80 *89 = 872.2 . discus: v2 = 9.80 *69 = 676.2 . shot: v2 = 9.80 *21 = 205.8 . then for each, kinetic energy is (1/2) mv2 so . javelin: KE = (1/2) *0.80 * 872.2 = 348.9 Joules . discus: KE = (1/2) * 2.0 *676.2 = 676.2 Joules . shot: KE = (1/2) * 7.2 *205.8 = 740.9 Joules . Then for each, Work = finalKE = force * distance so . javelin: force = 348.9 /2.0 = 174.5Newtons . discus: force = 676.2 /2.0 = 338.1 N . shot: force = 740.9/ 2.0 = 370.5 N . Yes, air resistance is a big factor. Please Rate . Yes, air resistance is a big factor. Please RateRelated Questions
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