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HES 307 Biomechanics > 307 Exam 2 > Flashcards

307 Exam 2 Flashcards

1
Q

If curl is performed fast then what happens with time, velocity, acceleration, and amplitudes on a plot?

A

Time decreases and velocity doubles and acceleration x4 so the amplitudes are larger (nonlinear)

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2
Q

If curl is performed with longer forearms then what happens with time, velocity, acceleration, and amplitudes on a plot?

A

No change in time, velocity and acceleration double, there are higher amplitudes because there is a longer distance traveled

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3
Q

If there is an increased mass on the barbell then what happens with time, velocity, acceleration, and amplitudes on a plot?

A

The amplitudes have a greater distance between them, hills are larger and valleys are lower for the horizontal and we increase the weight constant (W) in the vertical direction; taller hills and bigger valleys around that constant line.

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4
Q

Inverse Dynamics

A

Start with kinematics, then kinetics (FBD), then what is actually happening in the muscles

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5
Q

Impulse

A

Vector quantity, area under force vs. time plot

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6
Q

Momentum

A

Inertia in motion, vector quantity, mass times COM velocity, momentum of an object remains constant unless there is a net non-zero external force or torque.

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7
Q

Newton’s second law relationships

A

Sum of the forces equals mass (must remain constant) times change in velocity all divided by change in time which also all equals mass times acceleration

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8
Q

Quasi static

A

Moving so slowly that you can assume acceleration equals zero, smaller hills and shorter valleys.

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9
Q

Biceps curl impulse-momentum relationship

A

Momentum and net impulse are zero because initial and final velocities are zero. The force of the hand is equal to the weight because time is non zero

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10
Q

Negative net impulse

A

We have negative net impulse in order to slow down the weight so the force of the hand is less than the weight of the barbell

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11
Q

Horizontal forces of a curl

A

Force of the hand in the x direction is equal to zero, because there is no weight component in the x direction

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12
Q

Force: Faster curl

A

Force of the hand is equal to the weight of the barbell. The force in the up phase is positive, down phase is negative, so during the whole rep the net force is zero because they are equal and opposite, initial and final velocities=0

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13
Q

Force: Longer forearms

A

initial and final velocities=0, force of the hand=Weight of the barbell

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14
Q

Force: Different mass of the barbell

A

Force of the hand still=weight of the barbell

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15
Q

‘Giving’

A

Reduce risk of injury because you increase the time so you decrease the force via the impulse momentum relationship

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16
Q

Follow through

A

The limb has a lot of momentum that you eventually want to stop so you increase the time it takes, decrease the force.

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17
Q

Linear Work and Power are both

A

Scalar quantities. you multiply vectors using the dot product and get a scalar product. can be positive or negative (scalars). For work you multiply force times displacement. For power you multiply force times velocity

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18
Q

Work is the area under

A

force vs. displacement curve, independent of time.

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19
Q

Work and object’s energy

A

positive work=increases energy of object

negative work=decreases energy of object

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20
Q

Polar form of work calculates

A

Total work done

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21
Q

Cartesian form of work calculates

A

Work done broken up into horizontal and vertical components

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22
Q

Polar approach for work includes

A

F and d are magnitudes, dcos(theta)= amount of d in the direction of F, cos(theta) makes the product positive or negative. At a 90 degree angle, no work done. Less than 90 degrees, positive work done. Greater than 90 degrees, negative work done

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23
Q

Tails of F and d

A

They are tied together, so the arrows are pointing in different directions outward from each other

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24
Q

Cross method of multiplication of vectors gives you

A

another vector

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25
Q

Power definition

A

rate of doing work (work/time)

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26
Q

Work is conceptually ______ while Power can be______

A

Work is conceptually an average value while you can have average and instantaneous power, no instantaneous work

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27
Q

Work of the biceps curl (up phase)

A

Fx=0 so the whole term Fxdx=0, work is purely positive and equal to the weight of the barbell

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28
Q

Work of the biceps curl (Down phase)

A

Fx=0 so the whole term Fxdx=0, Fy is positive and equal to the weight of the barbell but dy is negative and when you multiply those together you get negative work

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29
Q

Whole rep of work of biceps curl

A

Work=0, displacement (d)=0

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30
Q

Faster Curl for work

A

No change in work because Vf and Vi both =0

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31
Q

Longer forearms: Work

A

More work because displacement increases in both up and down phases but over whole rep=0

32
Q

Shorter forearms: work

A

Less work because displacement decreases in both up and down phases. But over entire rep, work=0

33
Q

Increase mass of barbell: work

A

More work because more force

34
Q

Decrease mass of barbell: work

A

Less work because less force

35
Q

How to read Work vs. time plot

A

How much work is done relative to the beginning of the movement, no instantaneous work

36
Q

How to get total work

A

Add together the horizontal and vertical components. in graph form, vertical direction dominates

37
Q

Faster curl: power

A

Increase power because you decrease time

38
Q

Slower curl: power

A

Decrease power because you increase time

39
Q

Longer forearms: power

A

More work because you increase the displacement so you increase power. But over the whole rep then power=0

40
Q

Shorter forearms: power

A

Less work because you decrease displacement so decrease power. But over the whole rep, power=0

41
Q

Increase mass: power

A

Increased work from increased force so increased power

42
Q

Decrease mass: power

A

Decrease work from decreased force so decrease power

43
Q

Total power plot (power vs. time) forces

A

Average force in the horizontal=0, Average force in the vertical= weight of bar. vertical direction dominates so the total looks like the vertical plot

44
Q

Assumption of work

A

Total work basically =vertical work

45
Q

Graphing power plots

A

You look for zero values in work vs. time plot and you drop them down to power vs. time plot

46
Q

Muscle contractions: work and power

A

Concentric contractions=positive work and positive power. Force and displacement are positive

Eccentric contractions=negative work and negative power. Force is positive but displacement is negative

Isometric = 0 work and 0 power because no displacement

47
Q

Muscle Force-Velocity-Power curve

A

Nonlinear decrease, more muscle force can be produced eccentrically, rep performed slower=more load, more forces. Muscles can’t produce much force when moving quickly. Can get power because you multiply force times time

48
Q

Linear Energy definition, scalar or vector, and units

A

Capacity to do/perform work (J=Nm=kg times m(squared)/s). Energy is a scalar value so no direction and can have positive or negative values

49
Q

Mechanical Energy

A

Kinetic, gravitational potential, potential strain (deformation)

50
Q

Net impulse of 1st half of the curl up phase

A

Positive value

51
Q

Average vertical force from the hand on the barbell during 1st half of the curl up phase

A

Greater than the weight of the barbell. (Force of the hand in the vertical direction minus the weight) times time=positive value

52
Q

Force of the hand in the horizontal direction during the first half of the curl

A

Zero. mvi and mvf both =zero so (Force of the hand in the x direction) times time=0 since time is nonzero

53
Q

Work done in the horizontal direction during 1st half of the up phase of a curl

A

Zero

54
Q

If you take the pause out of the curl what happens with the forces in the x and y directions?

A

Fy=still W of the barbell and Fx=0. This changes the acceleration, this will now have a big negative valley in the middle of the plot

55
Q

Faster Curl: KE

A

Nonlinear increase since you are increasing the velocity

56
Q

Longer forearms: KE

A

Increased velocity for longer forearms so this would also be nonlinear increases

57
Q

Different mass of the barbell: KE

A

Linear changes since mass is not squared in the equation: 1/2mv(squared)

58
Q

Gravitational potential energy faster/slower rep

A

No change because there is no change in the mass or the displacement of the bar

59
Q

Longer forearms: PEg

A

Large PEg since you have a larger height, linear increase

60
Q

Increased mass of barbell: PEg

A

linear increase from the increased mass

61
Q

Non-conservative energy release (Q) is always

A

POSITIVE

62
Q

Springs are where?

A

Externally in exercise equipment like bands and internally in biological materials like tendons and bones

63
Q

Hooke’s Law

A

F=-kx, the negative sign is telling us that k is opposite the direction of delta x (direction of displacement) in order to get back down to zero (restoring force, push or pull)

64
Q

Hooke’s law is similar to

A

Newton’s 3rd law

65
Q

Work(spring) is the area under

A

force vs. displacement curve

66
Q

F=kx graph

A

Linear, slope=k

67
Q

Average force needed to stretch a spring/band is equal to

A

half of the force, it is equal to half of the force applied

68
Q

Force to raise and lower an object are both

A

Equal to the weight

69
Q

When doing a curl in the horizontal direction, there is no change in

A

Gravitational Potential energy because there is no height change

70
Q

Spring Constant Units

A

N/m (newtons per meter)

71
Q

Impulse units

A

kg*m/s

72
Q

Momentum units

A

kg m/s, same as impulse

73
Q

Work Units

A

Nm or J or (kg m(squared)/s(squared))

74
Q

Power Units

A

Watts (W) or J/s or (kg m(squared)/s(cubed))

75
Q

power= work/time but it also equals

A

Fxvx+Fyvy for cartesian and Fvcos(theta) for polar

HES 307 Biomechanics (1 decks)

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