5. Projectile Motion

A frog leaves the ground with a speed of 15 m/s and stays in the air for 2.0 seconds. At what angle did the frog jump?

A golf ball is hit at ground level at an angle of 31.9° above the horizontal. Its range is 257 m over a level green. What was the magnitude of the golf ball's initial velocity?

Here is something to try at a sporting event. Show that the maximum height h attained by an object projected into the air, such as a baseball, football, or soccer ball, is approximately given by h ≈ 1.2t² m , where t is the total time of flight for the object in seconds. Assume that the object returns to the same level as that from which it was launched, as in Fig. 3–58. For example, if you count seconds and find that a baseball was in the air for t = 5.0 s , the maximum height attained was h = 1.2 x (5.0)² = 30 m . The fun of this relation is that h can be determined without knowledge of the launch speed v₀ or launch angle θ₀ . Why is that exactly? See Section 3–8.

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