A physicist is inside an elevator rising in a skyscraper. She is holding a ball

Question

A physicist is inside an elevator rising in a skyscraper. She is holding a ball at a height h = 2.1 m above the floor of the elevator.

a) She lets go of the ball while the elevator is rising at a constant speed of 4.6 m/s. How long does it take the ball to hit the elevator floor?

b) Now let's try a somewhat harder variation on this problem. Suppose instead that the elevator is accelerating upward with constant acceleration a = 1.2 m/s2 and that the upward speed of the elevator at the instant the ball is dropped, is 4.6 m/s. Now how long does it take the ball to hit the elevator floor, assuming once again that it is dropped from a height of 2.1 m?

Explanation / Answer

a)taking downwards positive u=-4.6 m/s , a=9.8 m/s^2 , s = 2.1 m using s = ut + 0.5 at^2 => 2.1 = -4.6t + 4.9t^2 t = 1.27 s ans. b) in this case all will remain same except that we have to take relative acceleration of ball with respect to elevator relative acceleration of ball with respect to elevator,a'=9.8-(-1.2) = 11 m/s^2 again using same equation with a=11 2.1=-4.6t+5.5t^2 t=1.16 s Ans.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

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