Force on Ice Skater's Hand: Calculate & Express as a Multiple of Hand Weight

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SUMMARY

The discussion focuses on calculating the horizontal force exerted by an ice skater's wrist on her hand while spinning. The skater, weighing 54.0 kg and making 2.50 turns per second, has a hand mass of 0.675 kg and a radius of 0.75 m. The force calculated using the formula F = m * r * ω² results in 125 N. To express this force as a multiple of the hand's weight, the correct approach is to divide the force by the gravitational force acting on the hand, yielding a dimensionless number.

PREREQUISITES
  • Understanding of circular motion dynamics
  • Familiarity with the formula F = m * r * ω²
  • Basic knowledge of weight calculation (mg)
  • Concept of dimensionless numbers in physics
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  • Learn about the relationship between force, mass, and acceleration
  • Explore dimensionless quantities in mechanics
  • Review examples of rotational dynamics problems
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Students in physics courses, particularly those studying mechanics and rotational dynamics, as well as educators seeking to clarify concepts related to force and motion.

Abarak
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Question
A 54.0kg ice skater spins about a vertical axis through her body with her arms horizontally outstretched, making 2.50 turns each second. The distance from one hand to the other is 1.5m. Biometric measurements indicate that each hand typically makes up about 1.25% of body weight.

Hand breakdown:
m = .675kg
r = .75m
\omega = 2.50\frac{rev}{s} = 15.707\frac{rad}{s}
F = 125N

Part A:
What horizontal force must her wrist exert on her hand?
I figured this one out by using F=m*r*\omega^2

Part B:
Express the force in part (a) as a multiple of the weight of her hand.

My Problem:
I am getting confused with "as a multiple". Pardon my lack of knowledge but I have no idea what they are asking for? I know the answer box is looking for a unit of weight (w).

Sorry about the "easy" question and thank you for taking time in reading my post.

-- Abarak
 
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I think you just want to divide the force on the hand by mg. Which would be the weight on the hand. A multiple of weight would not be a weight, but a dimensionless number.
 
Hey Dick,

Thanks for the help. I was able to get the correct answer.

Man, I could never do what you Homework Helper's do but it REALLY helps!

I am taking an online physics class right now and not having someone to talk to really sucks. If I need to ask my professor a question it takes days to get a response while I can get one here within hours or minutes.

-- Abarak
 

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