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KPE263 > L15-17;C12 > Flashcards

L15-17;C12 Flashcards

1
Q

Explain the following and how they differ:

Kinematics
Kinetics

A

Kinematics- explains what is occurring to the object (how fast, acceleration, etc)

Kinetics- Explains the ‘why’. Why can object is in motion

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2
Q

An objects natural tendency is to _______ _______

A

Preserve motion

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3
Q

_____ is a measure of inertia (also resistance to change motion)

_____ is the pull of gravity on a mass

A

Mass, weight

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4
Q

______ is the change of position over time. This formula is ____ over ____

A

Velocity,

Delta D over Delta T’

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5
Q

What is considered the “quantity of motion” ?

A

Momentum

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6
Q

What is the formula for momentum?

A

M=m x v

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7
Q

What is Newton’s first law with respect to kinetics?

A

The quantity of motion will stay unchanged unless there is an action

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8
Q

What is the conservation of momentum formula?

A

(m.v)f=(m.v)i

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9
Q

What will happen to momentum if no force is applied?

A

It will stay unchained

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10
Q

What is a force?

A

This is something that changes the momentum of an object.

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11
Q

Since mass is usually constant in kinetic problems, what must happen to velocity?

A

Velocity must be the factor that changes.

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12
Q

What is Newton’s second law with respect to kinetics?

A

A force is proportional to change in momentum per unit of time, F=ma

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13
Q

What do we observe when we see an accelerating body? (Force wise)

A

We view the net forces acting on the object

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14
Q

What is the impulse momentum relationship?

A

Since force is equal to mass x acceleration, and acceleration equals v/t, impulse is F•∆t=∆M=(m•v)f-(m•v)i

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15
Q

What is Newton’s third law with respect to kinetics?

A

Every action has an equal or opposite reaction

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16
Q

When standing, GRF _ mg

When leaving the ground and jumping, GRF __ mg

A

=, >

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17
Q

Explain the application to force plates during jumping:

Stiffer jumping-
Softer lading-

A

Stiffer jumping- creates more force, in a short period of time
Softer landing- creates less force, but takes more time (more beneficial for athletes and less prone to injuries)

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18
Q

Explain how joint shape influences landing.

A

Joint shape influences if the landing will absorb or produce more force. If we don’t change joint shape, the time is a lot shorter.

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19
Q

When do frictional forces occur?

A

Frictional forces only occur when external forces apply.

They also occur whenever two surfaces in constant attempt to move or cross each other

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20
Q

The reaction force only arises due to what other force?

A

The action force.

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21
Q

Resistance arises in the direction opposite to ______ ______

A

Impending force

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22
Q

Explain the formula of friction. Also provide it.

A

The magnitude of the frictional force is the product of the coefficient of friction and normal reaction force

Ff= μ•R [N]

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23
Q

For static objects, friction is ______ or ______ to applied forces
For dynamic objects, friction is ______ and _____ than maximal static friction

A

Equal, opposite

Constant, less

24
Q

μs is always ____ than μk

A

Greater

25
Q

What is linear momentum defined as?

A

The quantity of motion

26
Q

Explain linear momentum’s units, and how it’s calculated.

A

Linear momentum is a vector and measure by m•v and units are Kg•m/s

27
Q

Change in momentum is directly related to what law?

A

Newton’s first law

28
Q

Explain what elastic and plastic collisions are. What will happen to the energy during collisions?

A 
Elastic= objects collide and bounce off each other retaining shape 
Plastic= objects collide and stick together

Also all energy put in will be lost in some quantity over time due to deformation and friction.

29
Q

In these situations, velocity of the system is ________, therefore, relative velocities are the same after and before. What is the formula.

A

Conserved

(m1v1+m2v2)i= (m1v1+m2v2)f

30
Q

Explain what happens in plastic collisions

A

At least one object deform and does not regain original shape. Objects do not separate and velocity is not conserved

31
Q

During linear momentum, what instants are we mainly measuring?

A

We are looking at the instant in time where acceleration and mass relate to force

32
Q

When does impulse (F•∆t=∆M) only apply?

A

This only applies if a constant force is throughout

33
Q

What is mechanical energy? Scalar or vector? What’s it measured in?

A

Energy is the capacity to do work, it is a scalar and measured in Joules. It has two factors, potential and kinetic.

34
Q

True or false: objects not in motion still have potential to produce energy

A

True

35
Q

What is the formula for positional and deformational potential energy?

A

Positional: Mgh
Deformation: 1/2kx^2 (K is stiffness, x is distance deformed)

36
Q

What is kinetic energy?

A

Objects that have the capacity to do work. This is energy in motion.

37
Q

What is the formula for kinetic energy?

A

KE: 1/2m•v^2

38
Q

What is the difference between energy of position and energy of deformation?

A

Energy of position= gravitational potential energy (PE) of athletes whole body

Energy of deformation= strain energy (SE) in the resistance bands

39
Q

What is the energy conservation law?

A

In the absence of externally applied forces other than gravity, the total mechanical energy of a system remains constant.

40
Q

What is the conservation of energy equation?

A

PEf+KEf=PEi+KEi

41
Q

The ____ performed by externally applied forces other than gravity can _______ the energy

A

work, Change

42
Q

What is the work energy relationship equation?

A

W=∆E=∆PE+∆KE+∆TE

43
Q

What is mechanical work? Explain work of a force. What is the equation?

A

This is work done by a force or an object. Work of a force when Applied, displaces an object,. If the object is displaced, work is done.

W=F•∆p

44
Q

True or false: all forces do work. Explain.

A

False, only where the position of application undergoes displacement.

45
Q

True or false: work can be positive, negative, and zero.

A

True.

46
Q

Is work a scalar or vector?

A

Scalar

47
Q

What does positive and negative work mean?

A

Positive work- means object has gained energy
(Force does positive work when in same direction as displacement)
Negative work- means object has lost energy
(Force does negative work when against the opposite of displacement)

48
Q

What are the two rules for work?

A
  1. Time must elapse for work to be done (displacement must occur)
  2. Not all forces do work (no displacement in direction of applied force means negative work)
49
Q

Biomechanical work states that muscles produce two types of work. Explain them and what they’re called.

A

External work: muscles function together to do work on the environment
Internal work: muscles function together to do work to move our body segments

50
Q

What is mechanical power is it a scalar or vector? whats it units?What is the equation?

A

Power refers to the rate at which work is done. The amount of work performed over a given time interval: w/∆t

Work and power are scalar quantities measured in watts

51
Q

Energy can be _________, if energy of a system has changed the nthat means work has been ______

A

Transferred, done

52
Q

_____ is the process that will change the state of energy

______ is the state,

A

Work

Energy

53
Q

during running, GRF is _____ times the body weight

A

2-3x

54
Q

True or false: all bodies are attracted to one another and have a force proportional of M•a. This is inversely proportional to the square distance between them.

A

True

55
Q

What forces usually act on momentum?

A

Friction and air resistance

56
Q

Explain the coefficient of restitution. What happens if it’s closer to 1? To 0?

A

The coefficient of restitution dictates how a collusion will occur. More elastic, closer to 1. More plastic, closer to 0. Increasing impact, velocity, and temperature increases coefficient of restitution.

57
Q

What are the units for work and power?

A 
Work= joules 
Power= watts

KPE263 (12 decks)

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