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SC 7.1/8 test
SC 7.1 and chapter 8 test
| Question | Answer |
|---|---|
| any material that can flow and that takes the shape of its container | fluid |
| What can be a fluid? | liquids and gases |
| Why can fluids flow? | their particles move mroe easily |
| the amount of force exerted on a given area | pressure |
| What is the SI unit for pressure? | pascal |
| What is the force of one Pa? | the force of one newton exerted over one square meter (1 N/m^2) |
| How do fluids exert pressure? | evenly in all directions |
| pressure caused by the weight of the atmosphere | atmospheric pressure |
| Where are gases found in the atmosphere? | 80% of all gases are found within the first 10 km of the atmosphere |
| What is the gas activity at the top of the atmosphere | gases are almost nonexistent |
| What is an example of a pressure change? | popping your ears |
| Is atmospheric pressure greater at the bottom or the top? | the bottom |
| How is pressure in water? | pressure increases as depth increases |
| Why does water exert more pressure than air? | water is denser than air |
| What is the movement of fluids? | move from areas of high pressure to low pressure |
| Why does a tornado suck everything towards it? | air pressure in the center of a tornado is very low, so since air moves from H to L pressure, all the air outside is pulled towards the low pressure system like a vacuum |
| when a force causes an object to move in the direction of the force | work |
| When do you stop doing work on an object? | when you stop touching it |
| What is a symbol of work being done? | if an object has kinetic energy (energy was transferred) |
| Is applying force the same as doing work? | no, work only happens when an object is moved |
| If I pull a desk towards me, am I doing work on it? | no. work is only done if it's in the same direction!! |
| If I carry a bookbag, is work being done? | no, you are carrying the bookbag up and you are moving forward--different directions |
| If I bend down and pick up a sack, is work being done? | yes, since you are moving up and so is the sack |
| If I walk up a mountain, how much more work am I doing than if I were to scale it? | 0 J. You do the same amount of work just over a longer distance. |
| the rate at which energy is transferred | power |
| What does power measure? | how fast work happens |
| If a machine can do more work in a shorter time than another, what does the first machine have? | greater power |
| If I use a fan instead of a hairdryer, how much more energy am I using? | 0. Increasing power does not mean that the amount of energy needed will change. |
| a device that makes work easier by changing the size or direction of a force | machine |
| What two things can a machine change? | size or direction of a force |
| If I am using a machine, how does the machine do work? | you do work on the machine which does work on something else |
| the work you do on a machine | work input |
| the work done by the machine | work output |
| Using a machine vs by hand, which uses less work? | neither |
| What does a machine do when it does work on an object? | it applies a force (output force) through a distance |
| What do machines allow? | smaller force to be applied over a longer distance |
| What does the force distance trade-off say? | they are inversely related |
| the number of times a machine multiplies force; compares input force to output force | mechanical advantage (MA) |
| What MA is needed for a machine to help? | MA must be > 1 |
| Why can a machine with this MA help move things? | output is greater than input |
| What will an MA of < 1 generate? | reduces output force but increases the distance an object moves |
| Can work output be larger than input? Why? | no, because some work is used to overcome friction |
| a comparison f a machine's output with the work input | mechanical efficiency (ME) |
| What ME would an ideal machine have? | 100% ME |
| Why are ideal machines impossible? | every machine must use work input to overcome friction |
| has a bar that pivots at a fixed point called a fulcrum | lever |
| Where is the fulcrum in a first-class lever? | between the input force and the load |
| What does a first class lever change? | direction of input force |
| Where is the fulcrum in a second-class lever? | on the other side of the load and input force (traveling to the right) |
| Where is the fulcrum in a third-class lever? | on the other side of the input force and load (traveling to the right) |
| has a grooved wheel that holds a rope or cable, with a load on one end and input force applied to the other end | pulley |
| What is a fixed pulley? | an attached pulley which you can pull down on a rope to lift the other end |
| What is a movable pulley? | it can be moved |
| What is a block and tackle? | a fixed and movable pulley put together |
| How do you determine the MA of a block and tackle? | count the number of rope segments |
| two circular objects differently sized, one of which twists | wheel and axle |
| Why does turning the wheel result in MA > 1? | the radius of the wheel is larger than the radius of the axle |
| straight slanted surface | inclined plane |
| a pair of inclined planes that move | wedge |
| Is a short fat wedge greater in MA or a long thin wedge? | long thin |
| inclined plane wrapped in a spiral around a cylinder | screw |
| How do you know relatively how great the MA is of a screw? | the longer spiral and the closer the threads, the greater the MA |
| consisted of two or more simple machines | compound machines |
| Is the ME of compound machines higher or lower than those of simple machines? | lower because they have more moving parts and more friction to overcome |
| STUDY YOUR DIAGRAMS!!!!!!! AND READ THE CAPTIONS! |
Created by:
Tsarmina
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