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A ball is projected from the ground with speed v at an angle theta measured from the vertical. During flight it undergoes an elastic collision with a vertical wall and returns to the ground. What is the total time of flight of the ball?

1. 2v sin(theta) / g
2. 2v cos(theta) / g
3. v sin(2theta) / g
4. v cos(theta) / g

Correct answer: 2v cos(theta) / g

Solution

Since theta is from the vertical, the vertical component is v cos(theta); the wall does not change vertical motion, so total time = 2 v cos(theta)/g.

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