Stuntman Jackie runs off the roof of one building,
moving horizontally at speed **v**.
He flies across an alleyway of width **7.9 m**
and falls onto a staircase which is **12.2 m**
below his original position.
*Question 1*
How long is Jackie in the air?

Answer: The time it takes Jackie to fall 12.2 meters is - 12.2 m = vy * t - 0.5 * (9.8 m/s^2) * t^2 = - (4.9 m/s^2) t^2 Solving for time t, we find t = 1.58 s

*Question 2*
At what speed **v** must Jackie run to land exactly on the staircase?

Answer: His horizontal speed remains constant during flight, so 7.9 m = vx * t Solving for t, vx = 5.01 m/s

*Question 3*
What is Jackie's speed when he lands?

Answer: His speed is a combination of horizontal and vertical components: vx = 5.01 m/s vy = (-9.8 m/s^2) * (1.58 s) = 15.5 m/s Total speed is v = sqrt(vx*vx + vy*vy) = 16.3 m/s

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This page maintained by Michael Richmond.
Last modified Dec 18, 2001.
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Copyright © Michael Richmond. This work is licensed under a Creative Commons License.