Chap04-Solution

# Chap04-Solution - Chap4-HW1 Questions 7 An airplane flying...

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1 Chap4-HW1 Questions 7. An airplane flying horizontally at a constant speed of 350 km/h over level ground releases a bundle of food supplies. Ignore the effect of the air on the bundle. What are the bundle's initial (a) vertical and (b) horizontal components of velocity? a) v oy = 0 km/h, b) v ox = 350 km/h, (c) What is its horizontal component of velocity just before hitting the ground? There is no significant horizontal acceleration so v x = 350 km/h, (d) If the airplane's speed were, instead, 450 km/h, would the time of fall be longer, shorter, or the same? Same. Time of fall is determined by vertical acceleration and vertical initial velocity 9. Three paths are shown for a football kicked from ground level. Ignoring the effects of air, rank the paths according to (a) time of flight, Since they all rise to the same height, they all tie; (b) initial vertical velocity component, Since they all rise to the same height all tie (c) initial horizontal velocity component They have different horizontal initial velocities because their ranges are different: 3, 2, 1; (d) initial speed, greatest first: 3, 2, 1 Problems 17. A projectile is fired horizontally from a gun that is 45.0 m above flat ground, emerging from the gun with a speed of 250 m/s. (a) How long does the projectile remain in the air? Know that 2 0 2 1 at t v y y oy + + = Choose origin at initial position of ball so y o = 0 and y = -45 m Since the ball is fired horizontally 0 = oy v Therefore () s 03 . 3 m/s 9.8 - m 45 2 2 2 = × = = a y t (b) At what horizontal distance from the firing point does it strike the ground? Since there is no horizontal acceleration, t v x x ox = 0 = 758 m (c) What is the magnitude of the vertical component of its velocity as it strikes the ground?

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Chap04-Solution - Chap4-HW1 Questions 7 An airplane flying...

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