Usain Bolt, the fastest man in the world, stands at the beginning of an infinite

Question

Usain Bolt, the fastest man in the world, stands at the beginning of an infinite flight of stairs, waiting for a nearby cannon to shoot a tennis ball straight up into the air. If he can climb one flight of stairs every 3 seconds, each of which is 10m tall, and the cannon shoots the tennis ball with an initial velocity of 250m/s:
A. How many flights of stairs can he climb before he'll need to lean out the window to catch the ball?
B. What will the speed of the ball be when he catches it?

Assume that Usain Bolt never gets tired, and air resistance is negligible.

Explanation / Answer

A. Let he traveled a distance of x m. Then No. of stairs = x/10 Time taken = 3x/10. x = (250*3*x)/10 - (0.5*9.81*9*x^2)/100 =>(0.5*9.81*9*x^2)/100 = 74x =>x = 167.63 Number of flight of stairs = 16.763 B.Speed of the ball = v = 250-(9.81*3*(167.63/10)) = -243.33 that is 243.33 m/sec downwards.

Related Questions

Navigate

• Browse (All)
• Browse U
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.