Lecture 30 - Work Energy Theorem

Question 1

what is energy

Answer 1

the capacity or ability to do work

Question 2

what are examples of forms of energy

Answer 2

thermal, chemical, nuclear, electromagnetic and mechanical

Question 3

mechanical energy is measured in

Answer 3

Jules (J)

Question 4

kinetic energy is related to

Answer 4

a body’s motion (linear or rotational)

Question 5

linear energy is calculated as

Answer 5

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

Question 6

what is the equation of linear kinetic energy

Answer 6

EK = 1/2 m v^2

Question 7

rotational kinetic energy is calculated using

Answer 7

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

Question 8

what is the equation of rotational kinetic energy

Answer 8

E<K = 1/2 I w^2

Question 9

what is potential energy

Answer 9

energy of position or deformation

Question 10

what are the two forms of potential energy

Answer 10

gravitational potential energy

deformation energy / strain energy

Question 11

what is gravitational potential energy

Answer 11

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

Question 12

what is deformation energy or strain energy

Answer 12

energy stored in a body by virtue of its deformation

Question 13

mathematically describing deformation energy will depend upon

Answer 13

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

Question 14

what is the equation for gravitational potential energy

Answer 14

Ep = m g h

Question 15

what equation is for deformation energy

Answer 15

Es = 1/2 k change in x^2

Question 16

what is total mechanical energy (TME)

Answer 16

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

Question 17

total mechanical energy is a

Answer 17

scalar

Question 18

gravity is a what force

Answer 18

conservative force

Question 19

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

Answer 19

remains constant

(PE + KE) = C

Question 20

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

Answer 20

gravitational energy is at max

kinetic energy is 0

Question 21

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

Answer 21

gravitational potential energy is 0

kinetic energy is max

Question 22

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

Answer 22

max velocity = max kinetic energy

Question 23

as the ball ascends into the air what happens to energy

Answer 23

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

Question 24

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

Answer 24

bodys total mechanical energy will be conserved

Question 25

resultant force will be conservative if all

Answer 25

external forces are conservative

Question 26

a force is conservative if

Answer 26

it does no work around a closed path (motion cycle)

Question 27

is walking more efficient than running

Answer 27

it depends, walking more efficient than running at certain speeds

Question 28

what happens to force the faster you run

Answer 28

the faster you run, the more force you need to apply

Question 29

what is probably not a reason that we transition from walking to running

Answer 29

metabolic energy expenditure

Question 30

what is probably reasons why we transition from walking to running

Answer 30

• peak ground reaction force ?
• velocity of ankle motion ?
• the length of your leg ?

Question 31

what happens to the amount of force we develop as we increase speed when walking

Answer 31

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

Question 32

as our velocity increases the power consumption will increase, what is this limited by

Answer 32

limited by our leg length

Question 33

what is the power and speed curve like between running and walking and why

Answer 33

walking has an exponential curve and running is linear, as we are not limited by leg length in running

Question 34

why is there a transition from walking to running in terms of power and speed

Answer 34

there is a point where to continue to provide enough mechanical energy to maintain the pendulum it becomes more costly than the spring