Mechanical Systems Flashcards
Force
A push or pull
Has magnitude and direction
Measured in Newtons (N)
Work
Transfer of energy through motion
Requires a force and distance
Measured in Joules (J) (unit for energy)
How do you calculate work?
W=Fxd
How do you calculate force?
F=W/d
How do you calculate distance?
d=W/F
What does NM stand for?
Newtons x Meters which is the same as joules
How much is 1kg in newtons?
10N
How much is 100g in newtons?
1N
How much is 1m in cm?
100cm
Machine
A device for multiplying forces or changing the direction of a force
Can increase the speed with which work is done
Levers
A simple machine that changes the amount of force you must exert in order to move and object
What are the 3 parts of a lever?
Fulcrum
Load
Effort Force
Fulcrum
The pivot point of a lever
Load
The mass of the object being moved
Effort force
The force used to operate a lever
Class 1 lever
Fulcrum is between the effort force and the load
Seesaw, scissors, etc
Class 2 lever
The load is between the fulcrum and effort force
Nutcracker, wheelbarrow, etc
Class 3 lever
The effort force is between the fulcrum and load
Baseball bat, gold club, arms, legs, hockey stick, etc
What are some levers in the body?
Bones act as levers in the body
Joints act as fulcrum in the body
Muscles exert the effort force
Nodding your head, tiptoeing, etc
Inclined Plane
A simple machine
A ramp or slope
Force advantage (decreased effort needed by increasing distance)
Example of inclined plane
Lifting a box out of a vehicle vs pushing it down a ramp
distance from ground to vehicle= 1m
mass of box=10kg
Work= Force 100Nx 1m distance
Work=100J
5m inclined plane to move the box
Force= Work/distance
Force= 20N (much less force
Wedge
Simple machine
Triangular tool
Portable inclined plane
Used to separate objects or pieces
Used to hold objects in place
Used to lift
Axe
Pulley
Simple machine
Grooved wheel that carries a rope
Used to change the direction of the effort force
Used to lift objects with less effort (force advantage)
Wheel and axle
Simple machine
2 wheels of different diameters that turn together
Can produce a distance advantage or force advantage
Effort on wheel=force advantage
Effort on axle=s/d advantage
Door knob
Screw
Simple machine
Cylindre wrapped with an inclined plane
Provides a force advantage
Turns rotational motion into liner motion
Mechanical Advantage
A value that indicates how much a machine multiplied force or distance
How do you calculate mechanical advantage?
MA=Fo/Fi
MA force advantage
> 1
Trade off is speed or distance
Loses speed or farther distance
MA speed or distance advantage
<1
Trade off is force
What does MA=1 do?
Change of direction only
What affects the MA of the lever?
Changing the length of the arms
MA of a class 1 lever
MA=1 is fulcrum is exactly in the middle like a seesaw
MA<1 (speed/distance advantage) is fulcrum is closer to effort force like a catapult
MA>1 (force advantage) is fulcrum is closer to the load like a carjack
MA of a class 2 lever
Always a force advantage (MA>1)
Wheel barrow, nutcracker, etc.
MA of a class 3 lever
Always a speed/distance advantage (Ma<1)
Hockey stick, baseball bat, golf club, etc.
What is a fixed pulleys mechanical advantage?
MA=1
Provide a change of direction only
Draw a class 1 lever
Answer in booklet
Draw a class 2 lever
Answer in booklet
Draw a class 3 lever
Answer in booklet
Draw a fixed pulley
Answer in booklet
What is the force output?
The load
What is the force input?
The effort force
What is the mechanical advantage of a moveable pulley?
Ma>1
Provide a force advantage
Draw a moveable pulley
Answer in booklet
What hint could you use to help find the mechanical advantage of a pulley?
The amount of ropes attached to the load is the number of mechanical advantage
Do math to make sure though
Block and tackle (pulley)
Made of multiple pulleys working together
Used to lift a large load
What is a block and tackle’s mechanical advantage?
MA>1
Provides a force advantage
Force can be in any direction
What is the force input for a inclined plane?
The force needed to push the load up the ramp
Work input
The work you do
Work output
The work the machine does
How do you calculate work input?
Wi=Fi x di
How do you calculate work output?
Wo=Fo x do
What is always the output?
The load ( no matter what machine is being used )
Energy
Ability to do work
Work is done whenever a force causes an object to move
When work is done, energy is transferred or transformed
What are the 2 types of energy?
Kinetic energy
Potential energy
Kinetic energy
Energy of motion
Used by simple machines in motion
There a, energy is kinetic energy
Roller coasters dropping, pulling a rope of a pulley, pushing one end of a lever, pushing something up a ramp
Potential energy
Stored energy
Chemical potential energy (food, batteries)
Gravitational potential energy
Elastic potential energy
The law of conservation of energy
Energy can’t be created or destroyed only changed in form
Work is the conversion of potential to kinetic energy or kinetic to potential energy
Friction
A force that resists movement
Anywhere 2 surfaces rub against each other
Results in loss of energy due to heat
Prevented by using lubricants such as oil
Lubricants are used in machines like engines and gears
Efficiency
A value indicating how much energy is lost due to friction or heat
Expressed as a percentage
How do you calculate efficiency?
E=Wo/Wi x 100
Label do, do, Fi, Fo and calculate Wo Wi and Efficiency
Answer in booklet, use on of the questions in booklet
Gears
Rotating wheel like objects with teeth cut into the rim
Work together in groups called gear trains
Motion is transferred from one to the other
Changes the direction of force
Explain force in gears
The driver gear is force input
The follower gear is force output
Any gear in between the driver and follower is the idler
Idler gears allow for the follower and driver gear to turn in the same direction
What are the 3 types of gear trains?
Parallel gears
Multiplying gears
Reducing gears
Parallel gears
Driver and follower are the same size (same number of teeth)
Used to change direction only
MA=1
Multiplying gears
Large driver gear and smaller follower gear
Speedy advantage
MA<1
Reducing gears
Small driver and large follower
Force advantage
MA>1
Formula for MA of gears
MA= #teeth of follower divided by #teeth of driver
Speed ratio of gears
If a machine has different sized gear the smaller gear turns faster than the bigger one
SR is the difference between the two speeds of the gear
Reciprocal of MA
How do you calculate speed ratio of gears?
SR= #teeth driver divided by #teeth follower
When doing speed ratio everything is the opposite even force and speed advantage
MA<1 Force
MA>1 Speed
Pressure
A measurement of the amount of force citing over certain area
Pascals is the unit
How do you calculate pressure?
P=F/A
Pascal’s law
If you apply pressure to a fluid in a closed container, the fluid will transmit for same amount of pressure in all directions
Hydraulic systems
A mechanical system that uses liquid under pressure in a closed system to do work
Uses pistons of different sizes to create a force advantage
Pressure is the same e throughout the container
How do you calculate the Force in a hydraulic system?
F=PxA
MA of Hydraulic systems
A small amount of force can be applied to the small piston
Resulting in a large amount of force on the large piston
Pressure stays the same throughout the system
Examples of hydraulic systems
Brake systems
Cranes
Ferris wheel
Elevator
Snow plow
Backhoe
Log splitter
Forklift
Bucket trucks
Pneumatic systems
Use pressurized air to transfer force
Examples of pneumatic systems
Dentist drills
Hovercrafts
Air casts
Jack hammers
Staple guns
Pneumatic nailers
