Levers & Inclined Planes
Name and describe the 3 parts of a lever
Load = mass of an object that is moved or lifted by the machine
Fulcrum = a fixed point that supports the lever and is the point of rotation
Effort Force = the force exerted on the lever to make it move
The definition of a "gear" and what a group of 2 or more gears is called
Gear = a rotating wheel-like object with teeth around its rim
A group of 2 or more gears is called a gear train
The definitions of "kinetic energy" and "potential energy"
Kinetic Energy = the energy of motion
Potential Energy = stored energy
The formula to calculate "pressure" and the unit its measured in
Pressure = Force / Area
Pressure is measured in pascals (Pa) or kilopascals (kPa)
What is a "hydraulic system"? What is a "pneumatic system"?
Hydraulic systems use the force of a liquid in a confined space.
Pneumatic systems have air that pass through the device under high pressure and then escapes outside the device
The definition of "work" and the unit we measure it in
Exerting a force on an object and moving that object some distance in the same direction of the force
Work is measured in Joules (J)
The requirements for a device to be considered a "wheel and axle"
There needs to be 2 turning objects that are attached to each other at their centers (the "wheel" doesn't even need to be round)
The definition of "efficiency" in relation to machines
Efficiency tells you how much of the energy you gave to the machine was transferred to the load by the machine
How does safety equipment, such as helmets, protect you from pressure?
The equipment helps to lessen the force of a blow and the potential for injury by helping to spread the force over a larger area
Give examples of hydraulic and pneumatic systems in your body
A pneumatic system in your body is your respiratory system.
The definition of "mechanical advantage"
The comparison of the force produced by a machine to the force applied to the machine
OR
The comparison of the size of the load to the size of the effort force
The definition and formula for "speed ratio"
Speed ratio is the relationship between the speed of rotations of a smaller gear and a larger gear
Speed Ratio = (# of driver gear teeth) / (# of driven gear teeth)
How can you make a machine more efficient?
Machines can be made more efficient by reducing friction
Ex) less moving parts or adding a lubricant (like oil or grease)
What is a "closed system"? Give an example of this kind of system in your body.
A closed system is a self-contained collection of parts
Your circulatory system is an example of a closed hydraulic system
List the 2 essential characteristics of fluids that a hydraulic systems rely on
Hydraulic systems rely on a fluids incompressibility and their ability to transmit pressure
The 2 formulas used to calculate mechanical advantage of levers and inclined planes
MA = Load Force / Effort Force
MA = Effort Arm / Load Arm
What is a "block and tackle"?
A "block and tackle" is a combination of fixed and movable pulleys
Do we need friction for machines to work properly? Explain why or why not using an example.
Yes we need friction for machines to work properly.
Ex) your bike would slip if there was no friction between your tires and the ground; you would slip if there was no friction between your shoes and the ground
What is the relationship between mechanical advantage and the distance the load is moved in a hydraulic lift?
The larger your mechanical advantage gets, the more you need to increase your effort distance.
Ex) if your mechanical advantage is 9, you would have to increase the effort distance 9 times
What are "valves" and "pumps"?
Valves are movable parts that control the flow of a fluid by opening or closing
Pumps use automatic valves controlled by pressure to move fluids in a certain direction
Where are the fulcrum, load, and effort in each class of lever and what is their purpose?
Class 1 = EFL; used either for power or precision
Class 2 = ELF; always exerts a greater force on the load than the effort force that you exert on the lever
Class 3 = LEF; the load can be moved very quickly (but you must exert a greater force on the lever than the lever exerts on the load)
How do you calculate the mechanical advantage of a pulley?
You count the number of rope sections (not including the section you are pulling if you are pulling down)
The formula to calculate "efficiency"
Efficiency = [(work done by the machine on the load) / (work done on the machine by the effort force)] X 100%
What is Pascal's Law?
When pressure is applied to a confined liquid, that pressure is transmitted equally in all directions throughout the liquid
Describe how a hovercraft works
Powerful pumps draw in outside air and pump it out through holes in the bottom of the hovercraft.
A "skirt" around the bottom holds in enough air to support the weight of the craft above water or land.
Hovercrafts use propellers to drive forward and are steered by rudders.