Ball Bearing Speed Calculation in Elevator

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Homework Help Overview

The problem involves an open elevator moving upward with a specified velocity and acceleration, and a ball bearing that rolls off the elevator floor. The discussion centers around the calculation of the ball bearing's speed after it rolls off, considering the effects of gravity and the initial conditions of motion.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the initial conditions of the ball bearing's motion, questioning why the acceleration due to gravity (9.81 m/s²) is considered instead of the elevator's acceleration. There is also confusion regarding the terminology used in the problem, specifically the term 'flier' and its implications for the ball bearing's motion.

Discussion Status

The discussion is ongoing, with participants clarifying terms and exploring the implications of the ball bearing's initial upward velocity and subsequent downward acceleration. Some participants express understanding after further explanation, indicating a productive exchange of ideas.

Contextual Notes

There is a focus on the relationship between the ball bearing's motion and the elevator's motion, with assumptions about the initial conditions being questioned. The terminology used in the problem has caused some confusion, impacting the clarity of the discussion.

Fuzzykatecake
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An open elevator is moving with an upward velocity of
0.52ms-1 with an upward acceleration of 2.4ms-2. A ball bearing then rolls off the floor with zero horizontal speed. Determine the speeds of ball bearing and elevator 2s after the ball rolls off the floor.

Using v=u+at, speed of ball bearing
Answer given was
v=(-0.52)+(9.81)(2)I don't understand why the acceleration of ball is 9.81 and not acceleration of lift. Shouldn't the acceleration of ball be the same as lift as they are in contact?
 
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What do you think 'flier' refers to? (This is a genuine question, I don't know what it means here.) My guess is it means it rolls out of the elevator.
 
haruspex said:
What do you think 'flier' refers to? (This is a genuine question, I don't know what it means here.) My guess is it means it rolls out of the elevator.
I am so sorry! It's floor!
 
Fuzzykatecake said:
I am so sorry! It's floor!
So does that resolve your question?
 
haruspex said:
So does that resolve your question?
Wait.. Are u saying that the ball rolls OUT of the elevator and is free falling and that's why the a is 9.81. But it still has the upward velocity of lift.. But how is it possible?
 
When it rolls out of the lift, it is initially still traveling with an upward velocity of 0.52 m/s. It is then subjected to a downward acceleration of 9.8 m/s2.

Chet
 
Now I get it thanks:)
 

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