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grade 8 science > Unit 4 > Flashcards

Unit 4 Flashcards

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1
Q

what is work

A

ex. when you exert a force on an object and move that object some distance in the direction of the force you do work on the object.
the transfer on energy through motion

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2
Q

what is the formula for work

A

work = force times distance

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3
Q

what is work measured in

A

it is measured in units called joules

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4
Q

what is mechanical advantage

A

comparison of the force produced by a machine to the force applied to the machine

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5
Q

what is one key thing you should

know about mechanical advantage

A

the smaller the effort force compared to the load the greater the mechanical advantage.

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6
Q

what is the formula for mechanical advantage (Newtons )

A

Load arm/Effort force

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7
Q

what is the formula for mechanical advantage in (Cm or M)

A

Effort arm/ load arm.

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8
Q

what is speed ratio

A

the relationship between the speed rotations of a smaller gear and a larger gear is called the speed ratio

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9
Q

what is the formula for calculating speed ratio

A

Number of driver gear teeth/ Number of follower gear teeth

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10
Q

what are the 4types of pulleys

A

fixed pulley
movable pulley
block and tackle
compound pulley

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11
Q

what is a pulley

A

is a grooved wheel with a rope or a chain running along the groove.

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12
Q

the axle of the pulley acts like a what?

A

a fulcrum

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13
Q

what is a fixed pulley

A

is attached to something that does not move such as a ceiling.

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14
Q

what is a movable pulley

A

is attached to something movable

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15
Q

what are a block and tackle

A

a pulley system that is a combination of fixed and movable pulleys

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16
Q

what is a compound pulley

A

a combination of several pulleys working together

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17
Q

what is pascals law

A

change of pressure is transmitted evenly throughout a fluid

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18
Q

what is a hydraulic lift

A

is a mechanical system that raises heavy objects

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19
Q

what is a hydraulic lift used an?

A

a hydraulic lift uses fluid under pressure in a closed system.

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20
Q

what is a closed system

A

a system having a boundary that separates it from its surroundings

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21
Q

what is a example of a closed system

A

your body’s circulatory system

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22
Q

what is the formula for pressure

A

Force/Area

23
Q

what does Pascals law states

A

pressure is transmitted unchanged throughout the liquid

24
Q

what is one pascal of pressure in newtons

A

it is a force of one newton per square meter

25
Q

what is a hydraulic system?

A

a device that transmits an applied force through a liquid to move something else by means of pressure

26
Q

what are the two essential characteristics of a hydraulic system?

A

their incompressibility and their ability to transmit pressure

27
Q

what is a Pneumatic system?

A

a system in which a gas, such s air transmits a force exerted on the gas in an enclosed space

28
Q

what is an example of a hydraulic system in your body?

A

Our heart is an amazing hydraulic device

29
Q

what is an example of pneumatic system in our body?

A

the respiratory system in our body is a example of a pneumatic system because of the air entering and leaving the lungs.

30
Q

what is a subsystem?

A

when a simple machine is apart of a large system we call it a subsystem

31
Q

what is a simple machine ?

A

a single lever, a pulley, or a wheel and axle is a simple machine.

32
Q

what are the three combinations of levers in the backhoe?

A

called the boom, the dipper, and the bucket

33
Q

What type of class lever is the boom in the backhoe? and what is its job?

A

it is a class 3 lever that raises or lowers the dipper

34
Q

what type of class is the dipper and what is its job?

A

It is a class 1 lever that moves the bucket in and out.

35
Q

what is the bucket’s job and what type of class lever is it?

A

it is a class 1 lever that tilts to dig a hole and then empty its load of dirt or other material.

36
Q

what is a backhoe?

A

is a rotating assembly of three levers combined with a hydraulic system.

37
Q

what is kinetic energy?

A

the energy of motion

38
Q

what is an example of kinetic energy?

A

when you are moving the pedals of a bicycle, the motion of the pedals are called Kinetic energy

39
Q

what is potential energy?

A

Is stored energy

40
Q

what is an example of potential energy ?

A

our body is an example of potential energy

41
Q

what does the Internal combustion engine describe?

A

the way the engine works

42
Q

how many cylinders do Internal combustion engines usually have?

A

four, six, or eight pistons and cylinders.

43
Q

what are all the four steps of the Internal combustion engine?

A
  1. Intake stroke
  2. Compression stroke
  3. Power stoke
  4. Exhaust stroke
44
Q

what is the Intake stroke of Internal combustion engine?

A

the piston moves down the cylinder and draws in the fuel-air mixture fine droplets of gasoline mixed with air

45
Q

what is the Compression stoke in the Internal Combustion engine?

A

it is where the piston moves up. The fuel-air mixture is compressed into a smaller space.

46
Q

what is the power stoke in the Internal Combustion engine?

A

it is when the piston is almost at the top and a spark from the spark plug ignites the mixture Hot gases expand forcing the piston down. Energy is transferred from the piston to the wheels of the car.

47
Q

what is the exhaust stoke in the Internal Combustion engine?

A

the piston moves up again, compressing and pushing out the waste products left over from burning the fuel-air mixture.

48
Q

what is a hydrogen fuel cell?

A

a cell that fuels chemical reaction that uses hydrogen and oxygen from the atmosphere to make electricity

49
Q

what is a crankshaft?

A

a shaft that turns or is turned by a crank. a crank shaft turns the wheel of a automobile.

50
Q

what is a piston?

A

in a engine a disc shaped part that fits tightly inside a cylinder in which some force, such as steam pressure moves it back and forth or up and down

51
Q

what is a class 1 lever

A

is a lever in which the fulcrum is between the effort and the load

52
Q

what is the class 2 lever

A

a lever in which the load is between the fulcrum and the effort ex. Bottle opener

53
Q

what is a class 3 lever

A

a lever in which the effort is applied between the fulcrum and the load. eg. tweezers

grade 8 science (22 decks)

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