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# Ice Skating

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on 10 March 2015

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#### Transcript of Ice Skating

Jillie's Awesome Jump!

Newtons Three Laws
We estimate that Jillie moves at a speed of about 5 m/s before and after the jump. This means she's moving at a speed of 10 miles per hour. With this speed, we would expect her to reach a height of about 1.5 feet (.457 meters) into the air and reach a distance of 2.5 feet (.762 meters) from the point of takeoff to the landing.

Estimations/Kinematics
Kinematics Diagram
A normal force is present and important when Jillie glides along the ice. However, the normal force is not present DURING the jump, but rather right before her jump. The normal force (along with friction) will push Jillie off the ground and will allow her to make her jumps. Another force present is Jillie’s push-off force that essentially allows her to jump up in the air
Applications of Force
In figure skating, there is very little friction present when gliding. Friction is involved when Jillie transitions from backward to forward and pushes off the ice with her blade. She is attempting to propel herself forward while the blade acts against the ice to prevent her from slipping.

An estimate of Frictional force in this case is: Frictional Force = uFn = 0.0046 (62*9.8) = 2.79 N

Application of Friction
The momentum Jillie carries as she glides backwards into the jump equates to p = mv. In quantity, that should equal around p = (5 m/s)(62 kg) = 310 kg m/s. Since she is gliding on a frictionless surface, energy is also conserved. However, right before the jump she increases the friction between her blade and the ice, thus ending the conservation of energy.
Conservation of Energy/Momentum
Jillie's Awesome Jump In Slow Motion
The Physics of Figure Skating
Figure skating is a perfect example of physics in everyday life. The graceful movement of the skaters depends on a multitude of physical properties, including friction, momentum, rotation, and so many others.

In this presentation, we will be analyzing and discussing a specific jump performed by Jillie!

Introduction
Newton's First Law
Newton's Second Law
An object in motion stays in motion unless acted upon by an outside unbalanced force. This law explains the basic conception of why Jillie moves or stops moving on the ice. Friction would be the outside force that allows her to stop moving; she would need to increase friction between the blades of her skates and the ice in order for her to come to a stop.
The acceleration of an object is directly proportional to the magnitude of the net force and inversely proportional to the mass of the object, F=ma. This law explains the relationship between mass, force and acceleration: the heavier the skater, the slower the acceleration, and the larger the mass and smaller the force, the smaller the acceleration.
Newton's Third Law
For every action, there is an equal and opposite reaction. For example, when Jillie needs to perform a double in which she needs to jump and make two rotations in the air, she needs to apply a force down on the for the ice to push back on her and allow her to make the jump.
Direction of Jump
x-velocity
y-velocity
Jillie's mass: 65 kg
Jillie's height: 67 in
Involvement of Movement and Rotation
Movement: The video shows Jillie setting up for a double salchow, jumping into the air and rotating two times before landing backwards and gliding out.

Rotation: Rotation is present when Jillie performs a double salchow. She completes 1.5 rotations as she reaches the peak of the jump, and finishes the last half rotation before landing on the ice.

Angular Momentum
Angular momentum characterizes an object’s resistance to change in motion . A figure skater has very little frictional contact with ice, so her angular momentum is conserved.

F weight = mg
F weight = mg
Free Body Diagrams in Motion
F Normal
F Normal
Taking Off:
Landing:
Angular Momentum Spin
Angular Momentum
Angular momentum when starting a spin, L=r*m*v, is different from angular momentum while rotating in a spin or jump, L= Iw. The moment of inertia is I= m*r^2. The Law of Angular Momentum says that a lower moment of inertia equals a greater angular velocity.

F friction
F friction
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Press play to watch!
Press play on both videos!
Thanks for watching the presentation!
Please take a few minutes to complete a quick survey here by clicking on the link below:

http://goo.gl/forms/QHNpYmDA0I
At the beginning of the spin, Jillie has a high moment of inertia because her legs and arms extend outward from her body, increasing the radius. Towards the end of the spin, she pulls her arms closer to her body to decrease her moment of inertia and increase her angular velocity, thus increasing her angular momentum.
Angular Momentum Spin
Press play to watch!
RWA Reflection
Audience Responses:
RWA Reflection

Our audience response indicated learning by providing us with the correct answers to the questions we asked in the audience survey.
Our intention was to teach our audience the physics involved in figure skating. The audience response revealed that they understood how physical properties like friction, kinematics, etc. related to figure skating.
I am satisfied with our presentation and would not change anything about it.
I would not change anything about our questions because I think they were simple enough for the audience to understand, but difficult enough to require thinking.
This RWA project taught me to be more attentative to physics in everyday life. Having a basic understading of physics enables one to answer those questions that we ask ourselves with a child-like curiousity.