UNIT
6: Machines and forces
6.1.- Forces and their
effects
A
force is a push or pull.
Non contact forces act from distance. They
do not touch the object. The main examples are gravity and magnetism.
v Gravity.- It attracts all objects to the center of the Earth. Isaac Newton had his
theory of gravity which changed the world.
v Magnetics.- It exists between magnetic minerals and metals. All magnets have a north
pole and a south pole.
Ø
Contact forces
Two objects are in direct contact.
v Friction.- It is a forcé that makes objects slow down and stop. Example: ski.
v Buoyancy.- It is a force inside a liquid. Example: scuba diving.
Forces can make objects change shape (plasticine)
and change position (kick a ball).
-A simple
machine has a few o no moving parts.
- The load
is the object you want to move.
- The effort
is the forcé you apply.
- There are six
types.
Ø A wedge.-It is made up of two inclined planes put together.
Ø A pulley.-It is made up of a rope and one or more wheels.
Ø A screw.-It consists of an inclined plane that goes around a cylinder.
Ø A Wheel and axle.-An axel is in the center of a Wheel.
Ø A lever.-It is a bar that moves on a fixed point called a fulcrum.
6. 3.-Complex machines
- Complex
machines are made up of two or more simple machines. Example: a bicycle.
-
A bicycle is made up of a frame, handlebar, brakes, gears, pedals, and wheels.
-
People use all types of machines every day.
-
Machines have the following functions:
·
Mechanical.-For
moving an object.
·
Thermal.-For
heating.
·
Information
processsing.-For processing and transforming
information.
-Machines need the energy to work such as water, The Sun, gas, and oil.
6.4.-Inventions and
discoveries
There are inventions and discoveries from the past.
-
They
improve medicine, entertainment, information, and better communication.
-
Examples
are penicillin, the Wheel, TV, and
X-ray.
- Technology improves everything but technological devices can cause problems.
