chapter 9 test Flashcards

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1
Q

what is conserved?

A

mechanical energy is conserved when there is no net work done by external forces

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2
Q

Kinetic energy equation

A

KE= 1/2 mv^2

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3
Q

Gravitational Potential Energy equation

A

PE = mgh

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4
Q

Spring potential energy equation

A

PE = 1/2 kx^2

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5
Q

What does the term mechanical energy refer to?

A

the sum of a systems kinetic and potential energy

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6
Q

positive work is…

A

is done by a force PARALLEL to an objects displacement

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7
Q

negative work is …

A

is done by a force ANTIPARALLEL to an objects displacement

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8
Q

when a force is acting perpendicular to an object displacement …

A

no work is done

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9
Q

what type of quantity is work?

A

scalar because it can be positive or negative but it does not have a direction

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10
Q

in a force vs. displacement graph what is the work?

A

the area underneath the graph

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11
Q

power

A

the amount of work done in one second, or energy used in one second

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12
Q

power equation

A

P = w/t

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13
Q

unit for power

A

watts

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14
Q

unit for work

A

joules

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15
Q

what does the mechanical advantage of a simple machine tell you?

A

how much the input force is multipled to give you the output force

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16
Q

whats the MA of a pulley?

A

the number of supporting tensions

17
Q

in an ideal simple machine the …

A

work in equals the work out

18
Q

the efficiency tells you…

A

how much energy is lost in any process for a simple machine

19
Q

what is the percent of efficiency in an ideal simple machine?

A

100%

20
Q

energy

A

the ability to do work

21
Q

potential energy

A

the energy of a position/shape/ or configuration

22
Q

elastic potential energy

A

potential energy that is stored in a spring or other elastic material

23
Q

what are examples of simple machines?

A

lever, pulley, wedge, inclined plane, wheel, axel, screw

24
Q

what does a simple machine do?

A

augments or multiples an applied force

25
Q

pulley

A

a simple machine that can change the direction and multiply an applied force

26
Q

efficiency equation

A

e = work out/ work in x 100%

27
Q

in most real-life simple machines…

A

some input work is lost due to friction so the work in does NOT equal the work out , and the efficiency is less than 100%