Homework Help: Physics

Posted by Priscilla on Sunday, February 19, 2012 at 9:53pm.

1. While riding on an elevator descending with a constant speed of 1.5 m/s, you accidentally drop a book form under your arm.
(a) How long does it take for the book to reach the elevator floor, 1.2 m below your arm?
(b) What is your book's speed relative to you when it hits the elevator floor?

2. To celebrate a victory, a pitcher throws her glove straight up-ward with an initial speed of 6.0m/s.
(a) How long does it take for the glove to return to the pitcher?
(b) How long does it take for the glove to reach its maximum height?

1a)

v = 3 m/s
h = 1.2 m
t = ?
Vf = ?

V = Vi + at
3 m/s = 0 + (9.8 m/s^2)(t)
t = .30 s

1b) Vf = Vi + at
Vf = 0 + (9.8m/s^2)(.30 s)
Vf = 2.94 m/s

2a & b)
Vi = 6 m/s
t1 = ?
t2 = ?

I'm really confused with this problem since only one quantity is given. But I dont think we can assume that final speed is 0 m/s.

Physics - drwls, Sunday, February 19, 2012 at 10:11pm
1. The answer is the same as it would be in nonmoving elevator
(a) t = sqrt(2H/g) = 0.495 s
(b) V = sqrt(2gH) = 4.85 m/s

2. (a) 2 Vo/g
(b) Vo/g
Vo = 6 m/s
g = 9.8 m/s^2
Physics - Priscilla, Sunday, February 19, 2012 at 10:53pm
Thank you very much.

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