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Physical Science > Work and Machines > Flashcards

Work and Machines Flashcards

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1
Q

work

A

a transfer of energy that occurs when a force makes an object move (force acting through a distance)

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2
Q

for work to occur…

A

there must be a force causing an object to move in the direction of the applied force

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3
Q

equations & units (work)

A

work = force x distance
force = work/distance
distance = work/force

work - joules (J)
force - newtons (N)
distance - meters (m)

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4
Q

conditions for work

A

force, cause, displacement

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5
Q

work and energy are related since…

A

energy is always transferred from the object doing the work to the object the work is done on

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6
Q

power

A

the amount of work done in a certain amount of time; rate at which work is done

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7
Q

equations & units (power)

A

power = work/time
work = power x time
time = work/power

power - watts (W)
work - newtons (N)
time - seconds (sec)

  • energy can also substitute for work
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8
Q

as force goes down…

A

distance goes up

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9
Q

machine

A

a device that makes doing work easier

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10
Q

what do machines do to make work easier?

A

they can change applied force and/or the direction of the applied force.

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11
Q

the same amount of work can be done by…

A

using more force, less distance or using less force, more distance.

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12
Q

machines help move things that…

A

resist being moved.

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13
Q

input force/effort force

A

the force applied to the machine

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14
Q

output force/resistance force

A

the force applied by the machine in order to overcome resistance

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15
Q

the amount of energy transferred to an object from the machine cannot be…

A

greater than the amount of energy transferred to the machine.

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16
Q

some energy is transferred into…

A

heat energy due to friction.

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17
Q

an ideal machine with no friction would have…

A

the same work input and output.

18
Q

efficiency

A

the measure of how much work put into a machine is changed into useful output work by the machine.

19
Q

efficiency equation

A

work output/work input x 100 = __%

20
Q

the efficiency of a machine is always

A

less than 100%

21
Q

what can make a machine more efficient and how?

A

lubricants, reducing friction

22
Q

nemesis of work is…

A

friction.

23
Q

efficiency relates to the law of conservation of energy because

A

you can never get more work from a machine than what you put in.

24
Q

mechanical advantage

A

the amount of times a machine multiplies the input force (no unit)

25
Q

two types of mechanical advantage (equations)

A

AMA - force output/force input

IMA - distance input/distance output

26
Q

how can you manipulate a lever to change MA

A

the longer the input arm, the greater the MA

27
Q

simple machine

A

machine the uses only one movement for work

28
Q

compound machine

A

machine that is a combination of two or more simple machines

29
Q

inclined plane

A

a sloping surface used to reduce force required for work

30
Q

lever

A

a bar that is free to pivet around a free point called a fulcrum

31
Q

first class lever

A

fulcrum is between input and output

nothing is multiplied

32
Q

second class lever

A

output is between fulcrum and input

MA > 1

multiplies force

33
Q

third class lever

A

input is between fulcrum and output

MA < 1

distance is increased

34
Q

screw

A

an inclined plane wrapped around a cylindrical post

35
Q

wedge

A

an inclined plane with one or more sloping sides

36
Q

pulley (first class lever)

A

grooved wheel with a rope, simple chain, or cable running along the groove

37
Q

block and tackle system

A

a system of fixed and moveable pulleys

38
Q

inclined planes (ex.)

A

inclined plane, wedge, screw

39
Q

pulleys (ex.)

A

wheel & axel, pulley, lever

40
Q

fixed pulley

A

attached to something that doesn’t move, force isn’t multiplied but the direction is changed, IMA & AMA of 1

41
Q

moveable pulley

A

MA of 2, multiplies force, one end of the string is fixed but the wheel is free to move

Physical Science (5 decks)

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