An object with a mass of 40.0 kg is fired with an initial speed of 1.24 Incorrec

Question

An object with a mass of 40.0 kg is fired with an initial speed of 1.24 Incorrect: Your answer is incorrect. Can you obtain an expression for the total energy of the object at its maximum height? Can you write an expression for the work done on the object by air resistance as it travels to the top of its trajectory in terms of the total energy and the maximum height and the total energy at the launch site? J (c) What is the speed of the projectile immediately before it hits the ground if air resistance does one and a half times as much work on the projectile when it is going down as it did when it was going up? m/s Correct: Your answer is correct. J (b) If when the projectile is at its maximum height of y = 326 m, it is traveling 87.9 m/s, determine the amount of work that has been done on the projectile by air resistance. multiply.gif 102 m/s at an angle of 30.0½ above the horizontal from a 166-m-high cliff (take ground level to be y = 0 m). (a) Determine the initial total mechanical energy of the projectile.

Explanation / Answer

part A:

initial Mech Energy Ui = KEi + PE i

Ui = 0.5 mv^2 + mgh

Ui = 0.5 * 40 * 124*124 cos 30 + ( 40 * 9.81 *166)

Ui = 3.31 *10^5 Joules

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b. total Mechnical Energy U = net Work Done

Work Done W = (mgh + 0.5 mv^2)

W = (40 * 9.8 * 326 ) + ( 0.5 * 40 * 87.9 *87.9)

W = 2.82 *10^5 Joules

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apply 0.5 mv^2 = 2.82 e 5

v^2 = 2.82e5 * 2/(40)

v^2 = 14100

V = 118.7 m/s

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