Elevator going down and you drop a book

[kmiller]

Homework Statement

While riding on an elevator descending with a constant speed of 3.3 m/s, you accidentally drop a book from under your arm.
(a) How long does it take for the book to reach the elevator floor, 1.1 m below your arm?
s
(b) What is the book's speed (relative to the earth) when it hits the elevator floor?

The Attempt at a Solution

4.9m/9.8m/s2=14.7
squareroot 14.7=3.834=answer a

1.1m+1/2(13.1)t
t=7.65
1.1m/7.65s=.1437=answer b

both of these answers were wrong. what equations am ia supposed to use?
how do i start?

 

[Kurdt]

For the first part it looks as though you're trying to use the correct equation but I have no idea where you got your numbers from?

For part b it will just be the speed of the elevator added to the speed you work out from standard kinematic equations.

 

[baba89]

As a scientist, it is important to first identify the relevant physical principles and equations that can be applied to this scenario. In this case, we can use the equations for kinematics, specifically the equations for motion with constant acceleration. The relevant equations are:

1. Distance traveled, d = v0t + 1/2at^2
2. Final velocity, vf = v0 + at
3. Average velocity, vavg = (v0 + vf)/2

In this scenario, we can assume that the book is initially at rest (v0 = 0) and is dropped from a height of 1.1 m. We also know that the elevator is descending with a constant speed of 3.3 m/s, so the acceleration due to gravity (a) is equal to 3.3 m/s^2.

(a) Using the first equation, we can solve for the time it takes for the book to reach the elevator floor:

1.1 m = 0 + 1/2(3.3 m/s^2)t^2
t = √(2(1.1 m)/3.3 m/s^2) = 0.67 s

Therefore, it takes 0.67 seconds for the book to reach the elevator floor.

(b) To find the book's speed when it hits the elevator floor, we can use the second equation:

vf = 0 + (3.3 m/s^2)(0.67 s) = 2.21 m/s

This means that the book's speed (relative to the earth) when it hits the elevator floor is 2.21 m/s.

It is important to carefully select and apply the correct equations and units in order to obtain accurate and meaningful results in any scientific calculation.