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15 Cards in this Set
- Front
- Back
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Formula For Vertical GRFs During Walking
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F=ma
Acceleration - gravity in vertical direction (constant) Can then calculate mass (weight) from known vertical force |
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Vertical GRFs During Running:
Action Peak & Passive Peak |
A: tpeak >100ms (weight acceptance)
P: tpeak =20-30ms (heel contact) |
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Amount of Forces Dissipated For:
- Walking - Jogging - Sprinting - Gymnastic Loading |
W - 1.2
J - 2-3 S - 3-4 G - 8-10 If you know these force values, you can use the acceleration constant to determine weight (F=ma) |
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Definition/Formula of Impulse
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Impulse is the area under the force-time curve
impulse=force x time units: Nsec |
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If the average force in the figure is 1.3 kN and the time of application is .29 s - what is the impulse?
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Can determine force you are exerting based on the time it is alotted - Linear impulse = force x time
1 kN = 1000 N 1.3 x .29 x 1000 = 377 N.sec |
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Definition/Formula of Linear Momentum
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Momentum is the quantity of motion that something possesses
Momentum (G) = mass x velocity units: kg m/s |
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Definition/Formula of Angular Momentum
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Momentum (H) = inertia x angular velocity
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How do we produce a change in Momentum?
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apply an impulse
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Newton's Second Law: F=ma can be changed to F= m x (v/t)
What is the alternate version of this formula and what does it mean? |
F x t = m x v
F x t = impulse m x v = momentum Therefore, impulse = momentum |
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Revised Newton's Second Law
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the application of an impulse will result in the change of momentum of a system
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Using Impulse During Gait
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- impulse is initiated during AP GRF as a braking force towards momentum during midstance and then attempts propulsion to gain momentum again
- braking impulse = propulsion impulse for a balanced gait |
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Impulse Effects on COM
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impulse accelerates COM - constant cycle of speeding up and slowing down
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AP GRFs During Gait
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Know Graph!
represents a sine curve with an amplitude of 25% BW total impulse of AP direction for a full gait cycle should be zero, as the impulse is equal to the change in momentum in order to have a balanced gait cycle |
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Walking at a Constant Speed = _______ impulse
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no net
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Medial-Lateral GRFs and the Deflection Direction During HC and Stance
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HC: medial deflection
Stance: lateral deflection |
