Elevator and dropped book

In summary, the problem gives us the initial velocity of -3.2 m/s and the change in height of 1.0 m. We can use the constant acceleration equation, yf = yi + vi(t) + (1/2)a(t)^2, to find the final position of both the elevator floor and the book. Since they both end up in the same final position, we can set the equations equal to each other and solve for t. Once we have t, we can use the equation vf = vi + at to find the final velocity of the book.
  • #1
caksez.14
5
0
While riding on an elevator descending with a constant speed of 3.2 , you accidentally drop a book from under your arm.How long does it take for the book to reach the elevator floor, 1.0 below your arm?
 
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  • #2
You need to show some formulas and some kind of attempt at a solution before you can receive assistance.
 
  • #3
I can't solve the problem how can I attempt at a solution??
 
  • #4
What is going on in the problem?
- Constant acceleration (due to gravity)... Here are your constant acceleration equations:

vf2=vi2+2a(x2-x1)

vf=viat

Okay... So let's see what the problem gives you.

Firstly, you know that gravity accelerates things down at 9.81m/s2... That's what "a" is.

You know the initial velocity and the change in height (x2-x1) from the problem. Can you find vf?

Once you know vf, let's see if you can find t with the equations given...
 
  • #5
caksez.14 said:
I can't solve the problem how can I attempt at a solution??

Why do you think that? Did you not attend the class? Do you not have your textbook?
 
  • #6
time is 0.45 I found that then Of course I can found final velocity however my result is wrong. What is the book's speed relative to you when it hits the elevator floor? asks question
 
  • #7
We can't help you if you don't post your work!


Also, you erased the template provided. Why did you do that?

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On posting questions: Any and all high school and undergraduate homework assignments or textbook style exercises for which you are seeking assistance are to be posted in the appropriate forum in our Homework & Coursework Questions area

NOTE: You MUST show that you have attempted to answer your question in order to receive help. You MUST make use of the homework template, which automatically appears when a new topic is created in the homework help forums. Once your question or problem has been responded to, do not go back and delete (or edit) your original post..
 
  • #8
Show your work. How did you find time? How did you find velocity?

This is the formula for relative velocity. It says that the velocity of A equals the velocity of B plus the velocity of A with respect to B.

[URL]http://upload.wikimedia.org/math/2/f/5/2f5a92923c17aea5a83160b242065b10.png[/URL]
 
Last edited by a moderator:
  • #9
I'm finding velocity from 'vf2=vi2+2a(x2-x1)' as 5.5 m/s however this result is wrong...

our Vi should be 3.2
a=9.8
and x=1
 
  • #10
what is A what is B?
 
  • #11
Elevator
vi = -3.2 m/s
a = 0m/s2
yi(floor)=0m
Using the constant acceleration equation yf = yi + vi(t)=(1/2)a(t)2
Set up an equation for yf(floor)

Book

vi = -3.2 m/s
a = -9.81 m/s2
yi(book) = 1m

Using the constant acceleration equation yf=yi+vi(t)+(1/2)a(t)2
Set up an equation for yf(book)

________________________________________________
You know that the book and the floor are in the same final position at the end of the drop,right? I mean, the book rests on the floor so they must have the same yf. Knowing this, how could you solve for t after setting the equations above up with actual values?
 

1. How does an elevator's speed affect a dropped book?

An elevator's speed does not affect a dropped book. This is because both the elevator and the book are subject to the same gravitational force, causing them to accelerate at the same rate regardless of the elevator's speed.

2. What happens to a dropped book in an elevator that is accelerating upwards?

If an elevator is accelerating upwards, the dropped book will appear to fall slower than it would on the ground. This is because the elevator's acceleration is counteracting the force of gravity, causing the book to experience less acceleration.

3. Why does a dropped book appear to float in an elevator that is accelerating downwards?

In an elevator that is accelerating downwards, the book will appear to float because the elevator's acceleration is greater than the force of gravity acting on the book. This creates a sensation of weightlessness, as the elevator and the book are essentially falling at the same rate.

4. How does the weight of a book affect its motion in an elevator?

The weight of a book does not affect its motion in an elevator. The acceleration of the book is solely determined by the force of gravity acting on it, which is constant regardless of the book's weight. Therefore, a heavier book will fall at the same rate as a lighter book in an elevator.

5. Will a dropped book hit the floor at the same time as a book placed on the floor in an elevator?

Yes, both the dropped book and the book placed on the floor in an elevator will hit the floor at the same time. This is because they are both subject to the same gravitational force, causing them to accelerate towards the ground at the same rate.

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