Linear Impulse and Momentum Flashcards
How do the graphs defer between a squat with a pause and a squat without a pause when accelerating up?
When there is a pause there is a horizontal point that returns the weight to the body weight.
When there is not a pause, there is no horizontal line and the newtons shoot up above body weight.
What is linear impulse?
Product of average force and time
[N x s]
How do you find impulse on a force vs time plot?
Find the area under the curve
Can you have an instantaneous impulse?
No
How do you find net impulse?
The sum of the forces times the change in time
What is momentum also called?
Inertia in motion
What is the product for linear momentum?
Product of mass x COM velocity
Do impulse and momentum have the same units of Ns?
Yes
According to Newton’s first law, the momentum of an object will remain constant unless what?
A net non-zero external force and/or torque is applied
What is the momentum equation?
Mass x Velocity
When will velocity change (accelerate)?
When a mass changes
How did Newton come to his second law?
He realised that the force over time when mass is constant would be equal to its acceleration. So F=ma
Impulse momentum relationship
Sum of Force x change in time =
mass (velocity f - velocity i)
Over the first half of raising a weight, how does the force and weight compare? Is the weight accelerating or decelerating?
-Force must overcoming weight
-F>W
-Accelerating
Over the second half of raising a weight, how does the force and weight compare? Is the weight accelerating or decelerating?
-Weight overcomes force
-F<W
-Decelerating
Over the first half of lowering a weight, how does the force and weight compare? Is the weight accelerating or decelerating?
-Weight overcomes force
-F<W
-Accelerating
Over the second half of lowering a weight, how does the force and weight compare? Is the weight accelerating or decelerating?
-Force must overcoming weight
-F>W
-Decelerating
What is the average horizontal force applied from the hands during the complete up/down phase and entire rep?
0 N
How will net impulse on the BB be altered over each phase by performing the exercise?
Faster/slower
Longer/shorter forearms
Different BB masses
There will be no effect on net impulse by changing these because if it still starts and ends with 0 force, the net impulse will always remind the same (0)
What is the relationship between net impulse and change in momentum?
Net impulse equals the change in momentum.
In the context of Newton’s second law, what is replaced with average values?
Instantaneous values are replaced with average values.
What is the formula for average acceleration?
Change in velocity with respect to time.
If both initial and final velocities are 0, what is the net impulse?
Net impulse equals 0.
True or False: The average vertical force when raising or lowering an object equals its weight if initial and final velocities are zero.
True.
What must be true for the average vertical force while raising an object?
It must be greater than the weight during the upward acceleration phase.
What happens to the average force when lowering an object?
It must be less than the weight to start downward acceleration.
Fill in the blank: The average vertical force during the entire raising or lowering event is equal to the _______.
weight of the object.
What is the outcome of the average force when analyzing the first half of the up phase?
The average force is greater than the weight.
What is the average force in the second half of the up phase?
The average force is less than the weight.
What is true about the initial and final momentum during the down phase?
One will be negative and the other will be zero.
In horizontal motion, what is the equation of motion?
F = m * a (force equals mass times acceleration).
What is the net impulse in horizontal motion when both initial and final velocities are zero?
Net impulse equals 0.
What happens to the average force in horizontal motion during forward and backward movement?
The average force is equal to 0.
What is the implication of having zero velocity at the beginning and end of the horizontal movement?
Average force must be 0.
How do changes in speed affect the net impulse as long as initial and final velocities are zero?
Net impulse remains 0.
What effect does changing the weight of the barbell have on net impulse?
It does not change the net impulse as long as initial and final velocities are zero.
What must be true about the average force if the net impulse is zero?
The average force must average out to 0.
Fill in the blank: The average force in horizontal motion during a complete repetition is _______.
0.
True or False: The average force can be negative or positive during instantaneous movement.
True.
What is required to achieve a positive net impulse during the first half of the up phase?
The force in hand must be greater than the weight.
What must occur in the second half of the up phase to achieve a zero final momentum?
Average force in hand must be less than the weight.
What is the relationship between average force and weight of the barbell in vertical motion?
The average force in the hand is equal to the weight of the barbell in the vertical direction
If the weight of the barbell increases, the average force also increases.
What is the significance of having zero momentums at the beginning and end of a phase?
It indicates that the net impulse must be equal to 0
This implies that average forces in the horizontal direction remain zero.
How does altering the speed of a repetition affect average force?
It alters the average force nonlinearly
The relationship is affected by the change in velocity and time, leading to a non-linear relationship.
What happens to the average force in the horizontal direction during a repetition?
The average force in the horizontal direction remains 0
This is due to having zero velocity at the end of the first half of the phase.
What is the effect of longer forearms on the average force during a repetition?
Longer forearms result in a linear increase in average force due to greater vertical displacement
The time taken for the repetition remains constant.
What are the two linear changes that occur when the mass of the barbell is altered?
- Change in mass
- Change in weight
Both changes affect the average force required during the motion.
In the context of a body weight squat, what does the average ground reaction force equal during the down phase?
The average ground reaction force equals body weight
This holds true even when there is no pause in the motion.
How does removing a pause from a squat affect the average force during the phases?
The average force remains equal to body weight during both phases
The shape of the force profile may change, but the average remains constant.
What is the primary factor that affects the height of a jump?
The upward velocity at the moment of takeoff
Increasing the upward velocity will lead to a higher jump.
What is the relationship between average ground reaction force and jumping height?
Increasing average ground reaction force will increase jumping height
This is due to the mathematical relationship in the jump propulsion equation.
True or False: The average force during the up phase of a squat with a pause is different from one without a pause.
False
The average force is still equal to body weight regardless of the presence of a pause.
Fill in the blank: The average force in the hand during vertical motion is equal to the _______.
weight of the barbell
What happens to the average force in the hand if the barbell weight is decreased?
The average force decreases
This is a direct relationship based on the weight of the barbell.
How does velocity affect the average forces during a repetition?
Velocity changes nonlinearly affect average forces
Both delta T and velocity components alter the average force.
What is the relationship between mass and vertical jump performance?
Decreasing mass improves vertical jump performance by reducing the force that needs to be overcome during the jump
A lower mass means less weight to push against the ground.
What effect does increasing displacement during a jump have?
Increasing displacement extends the propulsion phase, increasing delta T
A longer propulsion phase can lead to higher jump heights.
What is the role of ground reaction force in jumping?
Higher ground reaction force early in the propulsion phase can lead to increased jump height
This is influenced by the eccentric load from a countermovement jump.
True or False: A higher ground reaction force always results in a higher jump.
False
While a higher ground reaction force is beneficial, it must be balanced with displacement and average ground force.
What is the impact of consciously trying to increase the range of motion in jumping?
It may decrease average ground reaction force on that day
Training over time to increase range of motion can lead to adaptations that improve performance.
What is ‘giving’ in the context of landing from a jump?
Giving refers to yielding to the direction of motion during landing to reduce impact forces
This is often done by flexing joints to increase delta T.
What is the relationship between impulse and landing techniques?
Increasing delta T through giving allows for a decrease in average ground reaction force
This helps manage momentum during landing.
Fill in the blank: Power is the rate of _______.
work
Power cannot exist without work being done.
What are the two types of products used in calculating work?
Scalar product and vector product
Work is calculated using the scalar (dot) product of force and displacement.
What is the unit of work in the SI system?
Joule
One joule is equal to one Newton times one meter.
True or False: Work can only be positive.
False
Work can be negative if the force and displacement are in opposite directions.
How is work defined in physics?
Work is the product of average force and the displacement in the direction of that force
This is a scalar quantity.
What happens to the average force during follow-through in sports?
Follow-through increases the time over which force is applied, allowing the average force to be reduced
This can lead to healthier movements and decreased injury risk.
What is the significance of follow-through in athletic performance?
It helps maintain momentum and reduces forces at the point of impact
Essential for effective throwing, kicking, and catching.
What is the formula for power?
Power = Work / Time
Power is a measure of how quickly work is done.
What does increasing time in a landing situation achieve?
It reduces the average forces experienced during landing
This can minimize injury risk.
What is the unit of work in the SI system?
Joule
A Joule is defined as a force of one Newton acting over a displacement of one meter.
Is work a scalar or vector quantity?
Scalar
Work can be positive or negative depending on the directions of force and displacement.
What does positive work do to energy?
Increases energy
Positive work increases the velocity of an object, thereby increasing its kinetic energy.
What is the formula for kinetic energy?
1/2 mv²
Where m is mass and v is velocity.
What effect does negative work have on energy?
Decreases energy
Negative work decreases the velocity and kinetic energy of an object.
What does the area under the force versus displacement curve represent?
Work done
This area is independent of time, as time does not appear in the work equations.
What two approaches can be used to calculate work?
Polar approach and Cartesian approach
The polar approach uses magnitudes and angles, while the Cartesian approach uses vector components.
What is the relationship between time and the calculation of work?
Independent of time
Work is calculated using average force and displacement, regardless of the time taken.
Fill in the blank: Work is defined as a force times the _______.
displacement
True or False: Time must always be included in the work equation.
False
Time does not appear in the work equation, making it independent of time.
What happens to kinetic energy when positive work is done?
It increases
Positive work increases the object’s velocity, thus increasing its kinetic energy.
