Transcript Forces & Motion

Technological Systems
• A bicycle is a system of simple machines. It is made up of
different components that work together. When we
combine simple machines together, we form mechanical
systems.
• Machines usually require inputs (things that enter a system)
in the form of energy or matter
• The machine then does work and a transformation process
happens
• Finally, the machine produces outputs (things that exit a
system) in the form of energy or matter
Example: the dishwasher
• Inputs?
Dirty dishes
Water
Electricity
Soap
• Outputs?
Clean dishes
Waste water
Heat
Sound energy
Simple Machines
Create a page size table. Add to your chart as we watch this video and refer to pages
412-417 in your text book.
Simple Machine
Characteristics/Function
The lever
Bar rests on a supporting post called a
fulcrum. One end has a load that is
lifted, on the other end you apply the
force.
The inclined plane
Spread the distance so it is easier to
move (lift) something. (ramp)
The pulley
Changes the direction of force. When
you pull down, the other end goes up.
Wheel fitted with a cord (or chain)
The wedge
Tool used to separate things. It pries
something apart.
The wheel and axle
2 parts wheel and axel. Allows you to
move something.
Mechanical Systems
• When simple machines are combined, a
MECHANICAL SYSTEM is formed
• When the same type of motion is transmitted
from one component to another without
changing form, we call it MOTION
TRANSMISSION.
• When the type of motion changes from one
component in a system to another, we call it
MOTION TRANSFORMATION.
Motion transmission
• Chain & sprocket
Motion Transmission
Chain and sprocket
• Connects components that are far
away from one another.
• The gears do not mesh together;
they are connected with a chain (or
sprocket)
Direction of
components
The sprockets inside the
sprocket will turn in the
same direction.
Reversibility
Yes
Motion Transmission
• Belt & pulley
Motion Transmission
Belt and pulley system
–
When building a belt and pulley
system, you must ensure:
1.
Pulleys must contain a groove where
the belt can fit
2.
The belt must adhere to the pulleys
3.
The smaller the pulley the faster it
turns
Motion Transmission
• Gears
Motion Transmission
Gear trains
•
Contains at least two gears that
meet and mesh together
Direction of Alternates from
components one gear to
another
Reversibility Yes
Motion Transmission
• Friction wheels
Motion Transmission
4. Friction gear systems
– Similar to gear trains yet less
efficient because the friction
gears can slip.
– The larger the gear the
slower the rotation
Motion Transmission
p. 419-422
Mechanism
Description
Chain and Sprocket
Connect things that are far away from
each other (gear and chain).Both
sprockets turn in the same direction.
Belt and Pulley
Two parts: pulley and belt. Pulleys inside
belt go in same direction. Smaller pulleys
will rotate faster.
Gears
They turn and fit into each other. Each
gear goes in the opposite direction.
Friction Wheels
Circular motion of one turns the other by
friction. They are like gears without
teeth.
Pulley
Changes direction of the force. When you
pull down, the other end goes up.
Motion Transformation
• Recall: When the type of motion is changed
from one component to another in a
mechanical system, the motion has
transformed.
Motion Transformation Systems
1. Rod & Crank
Motion Transmission
• Rod and Crank mechanism
– This is the mechanisms used
in pistons
Motion Transformation
• Cam & Follower
Motion Transformation
Cam and Follower
– Rotational motion changed to translation
motion
When building a cam and follower, you
must ensure that:
1. The follower must be guided in its
translational motion
2. The shape of the cam determines how the
follower will move
3. A device such as a return spring is usually
necessary to keep the follower in continual
contact with the cam.
Motion Transformation
• Rack & Pinion
Motion Transformation
• 1. Rack and Pinion
– Contains a rack (straight bar with teeth)
and a pinion (gear)
While building a rack and pinion you
must ensure that:
1. The teeth on the rack and on the pinion
must be identical
2. The system requires frequent
lubrification
3. The greater the number of teeth on the
pinion the slower the rotation
Motion Transformation
• Screw & nut
Motion Transformation
Screw gear systems (2 Types)
– Contains a screw and a nut
– Type 1: the screw is the driver
• Transforms rotational motion into
translational motion (e.g. jack to lift the car)
– Type 2: the nut is the driver
• Transforms translational motion into
rotational motion
Motion Transformation
p. 423-425
Mechanism
Connecting Rod and Crank
Cam and Follower
Rack and Pinion
Screw and Nut
Description
Discussion Questions
• What is the difference between motion
transmission and motion transformation?
• Give an example of each type of these
systems.