Angular momentum of a falling ball

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Homework Help Overview

The discussion revolves around the calculation and interpretation of angular momentum for a falling ball, focusing on the direction and magnitude of angular momentum in a physics context.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of angular momentum and question its correctness. There is exploration of the direction of angular momentum using vector cross products and the right-hand rule. Some participants seek clarification on the interpretation of direction in relation to a specific viewpoint.

Discussion Status

The discussion is ongoing, with participants providing feedback on calculations and engaging in dialogue about the direction of angular momentum. There is a mix of agreement and further questioning regarding the interpretation of directional terms.

Contextual Notes

Participants are navigating the complexities of angular momentum direction, particularly in relation to the observer's perspective, which introduces potential ambiguity in directional terms like left and right.

ac7597
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Homework Statement
Polly climbs to the top floor of her dorm, a height H=90 meters above the ground. She holds a ball of mass m=2 kg in her hand. She sticks her arm out a window facing East, so that the ball is d=0.77 meters away from the window. Polly then drops the ball.

Ignore air resistance

What is the angular momentum of the ball measured from the window at a time t1=0.7 seconds after Polly drops the ball? Provide both a magnitude and direction.

What is the angular momentum of the ball measured from the window at a time t2=1.8 seconds after Polly drops the ball? Provide both a magnitude and direction.

What is the angular momentum of the ball measured from the window at a time t3=2.4 seconds after Polly drops the ball? Provide both a magnitude and direction.
Relevant Equations
angular momentum(L) = (radius) * (mass*velocity)
(L) = (radius) * (mass*velocity)
velocity= 0+ (9.8m/s^2) (0.7s) = 6.86m/s
(L) = (0.77m) * (2kg*6.86m/s)= 1.05 kg*m^2/s
angular momentum points towards Polly
 
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is the calculation correct?
 
ac7597 said:
is the calculation correct?
Looks right. What do you get for direction now?
 
direction is perpendicular to the velocity of the body. Thus it is a horizontal direction: left
 
ac7597 said:
direction is perpendicular to the velocity of the body. Thus it is a horizontal direction: left
From Polly's view, yes.
 
Does it mean the direction is clockwise?
Apparently left, right, west, east is not correct.
 
ac7597 said:
Does it mean the direction is clockwise?
Apparently left, right, west, east is not correct.
She is facing East, so which direction is left?
 
North
 
  • #10
ac7597 said:
North
Right
 

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