Lecture 30 - Work Energy Theorem Flashcards

1
Q

what is energy

A

the capacity or ability to do work

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2
Q

what are examples of forms of energy

A

thermal, chemical, nuclear, electromagnetic and mechanical

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3
Q

mechanical energy is measured in

A

Jules (J)

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4
Q

kinetic energy is related to

A

a body’s motion (linear or rotational)

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5
Q

linear energy is calculated as

A

one half of the body’s (m) multiplied by the square of its velocity (v)

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6
Q

what is the equation of linear kinetic energy

A

EK = 1/2 m v^2

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7
Q

rotational kinetic energy is calculated using

A

the mass moment of inertia (I) of the body in motion and its angular velocity (w)

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8
Q

what is the equation of rotational kinetic energy

A

E<K = 1/2 I w^2

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9
Q

what is potential energy

A

energy of position or deformation

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10
Q

what are the two forms of potential energy

A

gravitational potential energy

deformation energy / strain energy

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11
Q

what is gravitational potential energy

A

the potential of a body to do work as a function of height (h) with respect to a reference surface, where g is gravitational acceleration

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12
Q

what is deformation energy or strain energy

A

energy stored in a body by virtue of its deformation

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13
Q

mathematically describing deformation energy will depend upon

A

the amount of energy will depend upon the material properties of the deformable body

i.e no single equation can describe the deformation of all bodies

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14
Q

what is the equation for gravitational potential energy

A

Ep = m g h

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15
Q

what equation is for deformation energy

A

Es = 1/2 k change in x^2

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16
Q

what is total mechanical energy (TME)

A

the sum of the linear kinetic, angular kinetic, and positional potential energy

17
Q

total mechanical energy is a

18
Q

gravity is a what force

A

conservative force

19
Q

when gravity is the only acting external force, a body’s mechanical energy is what

A

remains constant

(PE + KE) = C

20
Q

at the gravitational potential energy and kinetic energy when the ball is at the apex

A

gravitational energy is at max

kinetic energy is 0

21
Q

at the gravitational potential energy and kinetic energy when the ball hits the ground

A

gravitational potential energy is 0

kinetic energy is max

22
Q

in terms of the conservation of energy, when something has max velocity = what is said about kinetic energy

A

max velocity = max kinetic energy

23
Q

as the ball ascends into the air what happens to energy

A

gravitational energy increases and kinetic energy decreases because gravity is slowing the flight

24
Q

if the resultant force acting on a body is a conservative force then the

A

bodys total mechanical energy will be conserved

25
resultant force will be conservative if all
external forces are conservative
26
a force is conservative if
it does no work around a closed path (motion cycle)
27
is walking more efficient than running
it depends, walking more efficient than running at certain speeds
28
what happens to force the faster you run
the faster you run, the more force you need to apply
29
what is probably not a reason that we transition from walking to running
metabolic energy expenditure
30
what is probably reasons why we transition from walking to running
- peak ground reaction force ? - velocity of ankle motion ? - the length of your leg ?
31
what happens to the amount of force we develop as we increase speed when walking
when we get to a certain rate of force development that we can no longer maintain that amount of hip rotation we begin to run walking is restricted by hip rotation due to dual stance
32
as our velocity increases the power consumption will increase, what is this limited by
limited by our leg length
33
what is the power and speed curve like between running and walking and why
walking has an exponential curve and running is linear, as we are not limited by leg length in running
34
why is there a transition from walking to running in terms of power and speed
there is a point where to continue to provide enough mechanical energy to maintain the pendulum it becomes more costly than the spring