Unit 9 - linear kinetics

are torques adn force kinematics or kinetics?

kinetics

explain Newton’s first law

law of inertia: A body in its state continues at rest or a constant velocity unless and external force (gravity) acts on it

1. What is inertia

2. Inertia is directly proportional to an object’s ____

1. resistance to change in motion

2. mass

Explain why it is easier to push a car rather than a ship

car has less mass so there is less inertia to overcome

1. define mass

2. what are the units for mass?

3. how is mass different than density?

4. equation for density

1. quantity of matter

2. kg

3. density is how tightly packed together the matter is

4. density = mass/volume

1. explain the difference between a volleyball and a medicine ball

2. less dense means…

3. more dense means…

1. a medicine ball and a volleyball are the same size (volume) but the volleyball is less dense so it has less mass and the medicine ball is more dense so it more mass

does size (volume) tell you mass and inertia?

NO

explain newton’s second law

law of acceleration: force is proportional to mass and acceleration

when mass is high an object will accelerate ____(more/less) when a given given force is high

less

(vice versa is true also)

1. The ____ on an object determines the acceleration. How much acceleration is determined by the object’s _____ .

2. what is the equation that represents this?

3. relate the movement of the object to kinematics (hint: use acceleration)

1. force, mass

2. F = ma

3. read all bullet points on slide for answer

connect newton’s first and second law

see image

what is derived from F = ma?

impulse = Momentum

Momentum equation

mass * velocity

Impulse equation

force * time

derive impulse = momentum

see image

1. what is impulse?

2. TRUE OR FALSE: impulse will result in a change in velocity. explain

1. force applied over a certain period a time

2. true since impulse = momentum and momentum = m * v

explain two ways to stop the football player’s momentum (low velocity) by using impulse

see image and hope you can read my handwriting

Is GRF and impulse of a momentum?

Impulse

1. What can you find under the blue curve?

2. The area under the curve is equal to ____

1. vertical impulse (F * t)

2. momentum

impulse can be found using the area under the curve of what kind of graph?

vertical impulse component of GRF

1. Review: anterior/posterior GRF is…

2. how do you find propulsion and breaking impulse?

3. 0 on the graph is what phase?

4. breaking impulse is from ____ (concentric/eccentric) activation of ____ muscles

1. breaking (posterior) and propulsion (anterior), horizontal component of GRF

2. area under the curve (green and blue)

3. heel strike

4. eccentric activation of quads

1. how can you tell if the person is speeding up or slowing down?

2. how is this ^^^ related to momentum?

1. looking at the area under the curve

2. impulse is equal to momentum, and momentum equation is mass * velocity and mass isn’t changing so velocity must be

1. define momentum

2. equation

3. units

1. quantity of motion

2. mass * velocity

3. kg*m/s

1. what is the pattern for momentum and impulse?

2. explain it

1. impulse — momentum — impulse

2. see image (purple)

impulse — momentum — impulse pattern:

1. in phase 1, during take off ____ is applied to the body

2. That creates a ____. During flight phase this is _____(got rid of/preserved)

3. To stop, velocity is brought to zero by ____

4. what are two ways to bring velocity to zero?

1. impulse

2. momentum (velocity), preserved

3. another impulse

4. see image (very bottom)

explain the graph

idk man

1. explain newton’s third law

1. for every action there is an equal opposite reaction

1. what law can be applied to friction?

2. what are the two types friction. explain them

1. newtons third law

2. static (from a not moving object) and kinetic (moving object)

1. definition of static friction

2. equation for static friction

3. what do the variable mean

4. example of static friction

5. once you overcome static friction it is _____ (easier/hard) to keep the object moving

1. resists onset of movement

2. F_max = mew_s * R

3. see image for variable meanings

4. poking something and it doesn’t move bc you did not overcome the static friction

5. easier

1. definition of kinetic friction

2. equation for kinetic friction

3. what do the variable mean

1. resists ongoing movement

2. F_max = mew_k * R

3. see image

is static or kinetic friction larger

static is always larger

1. what will the force vector for leaning forward to push something look like?

2. why do you lean forward and down to push something

3. why is it easier to push something with carpet sliders?

1. see image (top right drawing)

2. so that you change the vertical and horizontal breakdown — you are changing how you apply the force

3. reduces the static friction therefore kinetic also goes down

curling…

understand this

this is a CMS graph showing the force-time curve (pretty sure the person was jumping but idk):

1. that means this graph is showing an ____

2. what does the dip in the graph represent between 1 and 2

3. explain the breaking phase

4. explain the propulsion phase

1. impulse

2. pressing down on the ground to make the velocity go up (before you jump)

3. not 100% sure but it has to do with GRF and pressing down on the ground to jump

4. 
   

1. during a jump is breaking phase concentric or eccentric?

2. during a jump is propulsion phase concentric or eccentric?

3. does velocity go up or down in concentric phase?

1. see image

2. see image

3. up

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