Solve: (a) (b) Reflect: At the maximum height But there because the ball still has its constant horizontal compo-nent of velocity. The horizontal range equation, can be used only when the initial and final points of the motion are at the same elevation. 3.20. Set Up: Take upward. Solve: (a) With in (b) With gives Then (c) Use the vertical motion to find the time in the air: gives Then 3.21. Set Up: Use coordinates with the origin at the ground and upward. At the maximum height Solve: (a) gives so (b) Use the vertical motion to find the time in the air. When the froghopper has returned to the ground, gives Then Reflect: when The total time in the air is twice this. 3.22. Set Up: Use coordinates with the origin at the ground and upward. Solve: (a) when gives so v0 5 v0 y sin u0 5 1.15 m / s sin 50.0° 5 1.50 m / s v0 y 5 v0 sin u0 v0 y 5 " 2 2 a y 1 y 2 y0 2 5 " 2 2 1 2 9.80 m / s 2 21 0.0674 m 2 5 1.15 m / s v y 2 5 v0 y 2 1 2 a y 1 y 2 y0 2 y 2 y0 5 0.0674 m v y 50 a y 52 9.80 m / s 2 . a x 5 0,
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