The masses of the javelin, discus, and shot are 0.80 kg, 2.0 kg,and 7.2 kg, resp
ID: 1721816 • 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 correspondingtrack events are about 89 m, 69 m, and 21 m, respectively. (a) Neglecting air resistance, calculate theminimum initial kinetic energies that would produce these throws. javelin 1 J discus 2 J shot 3 J(b) Neglecting air resistance, estimate the average force exertedon each object during the throw, assuming the force acts over adistance of 2.0 m. javelin 4 N discus 5 N shot 6 N
(c) Do your results suggest that air resistance is an importantfactor?
7 (a) Neglecting air resistance, calculate theminimum initial kinetic energies that would produce these throws. javelin 1 J discus 2 J shot 3 J
(b) Neglecting air resistance, estimate the average force exertedon each object during the throw, assuming the force acts over adistance of 2.0 m. javelin 4 N discus 5 N shot 6 N
(c) Do your results suggest that air resistance is an importantfactor?
7 javelin 1 J discus 2 J shot 3 J
Explanation / Answer
(a) in the given problem we can see that if aprojectile is launched, in the absence of air resistance with speedvi at angle above the horizontal the time required toreturn to the original level is found by the equation ofmotion y = viy t + (1 / 2)ay t2 0 = (vi sin) t - (g / 2)t2 t = 2 vi sin / g the range is the horizontal displaceemtoccuring in this time R = vxi t = vicos (2 vi sin / g) = vi2 (2sin cos) / g = vi2sin2 / g the maximum range occurs when = 45o vi2 = gRmax the minumum kinetic energy required to reacha given maximum range will be KE = (1 / 2) mvi2 = (1 / 2) m gRmax (a) solve for the minimum kinetic energy neededin the record throw of each object (b) the required force for each object is F = (KE - 0) / s = ....... N (c) yes if the muscles are capable of exerting....... N on an object and giving that object a kinetic energy of.......... J as in the case of the shot those same muscles shouldbe able to give the javelin a launch speed of vi = (2 KE / m) = ....... m / s Rmax = vi2/ g =............ m (a) solve for the minimum kinetic energy neededin the record throw of each object (b) the required force for each object is F = (KE - 0) / s = ....... N (c) yes if the muscles are capable of exerting....... N on an object and giving that object a kinetic energy of.......... J as in the case of the shot those same muscles shouldbe able to give the javelin a launch speed of vi = (2 KE / m) = ....... m / s Rmax = vi2/ g =............ m
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