Unit Overview
The topic of simple machines is used in
elementary school to introduce concepts related to
forces and motion. Forces that are applied to move an
object across a distance are considered to do “work.” A
machine is anything that makes it easier to do work,
that is, it reduces the amount of force needed. Simple
machines rely on humans to provide the force. At the
third grade level, students can be introduced to the
quantitative measurement of force, rather than using
only comparative measures (harder push, etc.). Students
can also begin to identify relationships between force,
mass, and distance, but they need not use mathematical
formulas to represent these relationships.
Students may have common
or everyday ideas about the meanings of work, force, and
machines that do not match the scientific definitions.
It is important to clarify these at the beginning of the
unit. |
Learning Objectives
Students will know
and experience:
- Scientists define work as
using a force to move an object over a distance.
- A force can be a push, pull,
or lift.
- It is possible to measure
force so that we can compare how much force it takes to move
different objects under different conditions.
- The amount of force that it
takes to move an object depends on the weight (mass) of the
object.
- Objects have weight (mass)
because of the pull of gravity.
- The amount of force that it
takes to push or pull an object across a surface is affected
by friction.
- Friction is a force caused
by two objects rubbing together
- A machine is something that
makes it easier for a human being to do work.
- Making work easier means
requiring less force to get work done.
- Simple machines require an
input of human force.
- Modern machines may do all
the work, so that human force is not necessary--the force or
energy is provided by electricity, fuel, etc.
- An inclined plane is a
simple machine that can be used to reduce the amount of
force needed to lift an object.
- The longer the inclined
plane, the less force required for lifting.
- In science investigations,
the outcome can often be affected by several things called
variables. For a “fair test or fair comparison” only one
variable can be changed at a time.
- Wedges and tools are simple
machines that are related to inclined planes and they can
make specific types of work easier.
- Levers are another type of
simple machine that can be used to help lift or “pry”
objects.
- The placement of the fulcrum
in a lever affects the height of the lever and the amount of
force needed to use it.
- There are several kinds of
levers; not all levers look alike and work alike.
- A wheel and axle system can
make it easier to move an object over a surface.
- Gears are connecting wheels
that can transfer motion from one place to another and can
change the direction and speed of motion.
- A pulley is a simple machine
that can make it easier to lift things, by changing the
direction of force and/or the amount of force needed.
Students will
practice:
-
Formulating questions on a specific science topic and
choosing the steps needed to answer the questions.
- Collecting
data for investigations using scientific process skills
including observing, estimating, and measuring.
-
Constructing charts and visualizations to display data.
- Using data
to produce reasonable explanations.
- Reporting
and displaying the results of individual and group
investigations.
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