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SCIENCE EXAM!!

Terms in this set (44)

How can a machine make work seem easier without changing the total amount of work you actually have to do?
It transfers force, changes the direction of the force, increases the magnitude of the force, or increases the distance or speed of a force.
Why does the total amount of work you put into a machine always have to be equal to or less than the total amount of work the machine does as a result?
Work can never be 100% efficient and friction reduces the work output compared to the work input.
How is an ideal (or perfect) machine different from a real machine, in terms of efficiency?
In terms of efficiency, a perfect machine would be 100% efficient while a real machine cannot be.
Describe a machine with a mechanical advantage of less than one. (How does it change your force/distance/direction?) Why would someone use this sort of machine? And then give a real world example.
3rd class levers will always have a mechanical advantage of less than one because its input force is less than its output force. A real-world example of this is a broom sweeping.
Describe a machine with a mechanical advantage of more than one. (How does it change your force/distance/direction?) Why would someone use this sort of machine? And then give a real-world example.
A machine with a mechanical advantage of more than one means that the load is further away from the fulcrum (input force more than output force). A real-world example of this is when only one person is on the see-saw and it is bent all the way to one side.
What can you do to increase the mechanical advantage of a lever?
If you move the load further away from the fulcrum you can increase it.
Explain ways you can increase the efficiency of a machine.
Reducing the amount of friction in a machine is a good way to increase the efficiency.
How does the mechanical advantage of a first-class lever compare to a second class and third class lever? Give examples of each type.
The mechanical advantage of a first-class lever compares to a second and third class lever because the load and the effort are equal so there is a mechanical advantage of 1. On the other hand, there is another version of a first class lever in which the input is larger than the output but this is an exception to the MA of 1 rule for FCLs.
How can you calculate work, power, efficiency and mechanical advantage? (What formulas do you need?)
MA: load/effort
Work: w=f*d
Power: f*d/time
Efficiency: output/input (as a percentage out of 100%)
What is the freezing and boiling points of water on the Fahrenheit scale? On the Celsius scale?
Freezing pt: 32˚F, 0˚C
Boiling pt: 212˚F, 100˚C
How does a thermometer work?
A thermometer is a glass tube filled partially with mercury and as the temperature around the glass heats up the liquid expands and rises in the tube, therefore increasing the visible temperature.
How is thermal energy different from temperature?
Thermal energy is different from temperature because while they both rely on kinetic energy, temperature is the average kinetic energy and thermal energy is the total kinetic energy in a substance.
What is absolute zero on the Fahrenheit scale?
Absolute zero: -459˚F
Describe how the movement of molecules and the spacing of molecules compare among solids, liquids, gases and plasmas.
In a solid, the molecules are close together with little to no movement. In liquids, the molecules are more spread apart, they've heated up, and they are moving more. In a gas, the molecules are very spread apart and very hot. They are also moving a lot. In plasmas, molecules are very hot and in an excited state, therefore moving around randomly and spread out.
Looking at the graph showing the heating curve of water below, can you explain what is happening at each point and on each line segment?
A: the water is quickly increasing in temperature
B: the heat is focusing on something else besides the water, therefore stalling the temperature increase.
C: the temperature begins to quickly increase again.
D: the water has reached a boiling point
E: the temperature has reached an outlying point.
F: the temperature stops increasing.
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