Lesson by Melissa Sparrow, Anna
Kapusta and Jenell Barkan
Motion and Forces
Lesson for:
- K through 2
Project description:
There are many things to be explored about the topic Motion & Forces and
many of them are hard to understand. For children in grades K through 2
many of the main points of this topic are:
- Objects change their motion only when a net force is applied.
- Whenever one object exerts force on another, an equal amount of
force is exerted back on the first object.
- Between any two charged particles, electric and magnetic force is
vastly greater than the gravitational force.
- Newton's three laws of motion: (1) A body at rest remains at rest
and a body in motion continues to move at constant speed along a straight
line unless, in either case, the body is acted upon by an outside force.
(2) An outside force acting on a body
causes the body to accelerate in the direction of the force; the
acceleration is directly proportional to the force and inversely
proportional to the mass of the body. (3) For every action there is an
equal and opopsite reaction.
- The benchmarks for understanding the motion of objects and repeating
patterns of motion do not demand the use of equations; a qualitative
understanding is sufficient.
- The fact that it took such a long time historically to identify the
laws of motion (Newton's Laws) suggests that they are not self-evident
truths.
- The earth's gravity pulls objects to the center of the earth.
- Center of gravity affects movement.
- Magnets move some objects.
- A magnet will point to the North Pole and conversely the opposite end
will point to the South Pole.
- Weight of an object affects friction between the object and what it
is setting on.
- Heavy objects will NOT fall faster than light objects due to
gravity's force.
- Heavy objects will fall with more force than lighter objects.
When children come to kindergarten they are not a blank slate but they
should have some understanding that things move, they can make things
move, and things fall to the ground when dropped. By the time children
leave second grade they should understand
things move in many different ways, such as straight, zigzag, round and
round, back and forth, and fast and slow. The way to change how
something is moving is to give it a push or pull. Things that make sound
vibrate. Things near the earth fall to the
ground unless something holds them up. Magnets can be used to make some
things move without being touched. Introduction to Newton's three laws
of motion.
The ideas of Motion & Forces are very difficult to understand, even
for adults. Students often have trouble relating formal ideas of motion
and force to otheir personal view of how the world works. Three of the
obstacles are (1) The fact that an object in motion will stay in motion
moving in a straight line forever without slowing down unless an outside
force acts upon it runs counter to what we can see happening with our
eyes. (2) Limitations in describing motion may keep students from
learning about the effect of forces. Students of all ages tend to think
in terms of motion or no motion. It is helpful to divide the category of
motion into steady motion, speeding up, and slowing down. (3) The
action-equals-reaction principle may be hard to grasp for some students.
To say that a book presses down on a table is sensible, but then to say
the table pushes back up with exactly the same force and that force
disappears when you pick the book up seems false.
Confusion may be caused by the word "speed" being used in English for
both frequency and velocity. Does a guitar string move quickly (back and
forth a thousand times a second) or slowly?
A fact that often causes problems for students is that the force of
gravity is weak compared to electric and magnetic forces. Gravity
becomes appreciable only when very large accumulations of matter
figure.
The term "gravity" may interfere with students' understanding because
it often is used as an empty label for the common notion of "natural
motion" toward the earth. The important point is that the earth "pulls"
on objects.
It may be difficult for students to realize the difference between the
speed and the force of falling objects dropped at the same time from the
same height.
Here are suggestions for teaching lessons in Motion & Forces.
MAGNETISM
Magnetism is a force that is stronger than gravity. A common
misconception about magnets is that they pick up all metals. Children
must be helped to understand magnets only pick up nickel, iron, and
cobalt along with their alloys; i.e., steel. A way to help to understand
this is by making a magnet board. To make a magnet board, fill an ice
cube tray with many different objects both magnetic and non-magnetic and
attach a magnet. Worksheets and other activities can be designed around a
magnet board.
Magnets work because of magnetic fields. Children should understand
that the metal atoms act like tiny magnets. To demonstrate this you can
have children make their own magnets. Run a magnet across a steel nail
in the same direction several times. After this is done try to pick up
paperclips with the nail. Then hit the nail with a hammer and try to
pick up paperclips again. This will show children magnetic fields can be
disturbed.
There are many different magnets and different magnets can be
different shapes, size, and strengths. Magnets are stronger at their
poles. That is why a horseshoe magnet is stronger than a bar magnet
because the poles are closer together. To demonstrate
this put a magnet in a bowl of paperclips. This shows children how
magnets attract more at their poles. Also children should be made to
understand that like poles repel and opposite poles attract. An activity
may be making bar magnets jump when two like poles are put together.
The earth is the strongest magnet. Its magnetic poles are the reason the
compass works. The North magnetic pole is located at the geographical
South pole and the South magnetic pole is located at the geographical
North pole. To make children think about this idea, ask why does the
North end of a compass point to the North pole of the earth? Shouldn't it
be repelled? Another activity involves making a compass. Hang a bar
magnet on a string so it is free to turn. Once it stops moving put a
chalk mark on the end pointing to the North Pole. Swing the magnet again
and see that when it stops moving the same end will always point to the
North pole and the opposite end will always point to South pole.
GRAVITY
Gravity is the force that pulls all things down toward the earth.
Without gravity, balls would fall up NOT down (Eg: Space). Gravitation
is the force between things that pull them together. The farther apart
things are the less gravitational pull. The
heavier an item is the harder earth's gravity has to work to pull the
item to it. However, the heavier the item is the more mass it has, this
makes the item more sluggish. Therefore these two opposing elements
cancel each other out and make a heavy and a light object fall at the
same rate.
The center of gravity is the point where all the weight of an object
acts. Our center of gravity is directly above our feet. To demonstrate
this have children sit in a chair with hands at their sides and feet in
front of the chair. Then have them try to get up: Can't be done. Now
have their arms extended forward and try to get up again: it is much
easier. Another activity that demonstrates how an object's center of
gravity affects an object's movement is by placing a small water balloon
inside a balloon that has been blown up and record how the ballon rolls
or flies through the air.
To change the center of gravity take seven books of about the same
size, and stack them on the edge of a table. Slowly start moving the
books forward until the first book is completely over the table. You
have just demonstrated changing the center of gravity.
To find the center of gravity on an irregular object, cut a shape out
of cardboard and attach a string with a fishing weight to one corner.
Trace with a marker the string, repeat the steps on another corner, where
the lines cross is the center of gravity.
Weight is how gravity is measured. The closer to the earth's center,
the heavier it is (mass or amount of matter doesn't change). Pose the
question: Would going to the top of a mountain help anyone lose weight in
the way people usually mean?
CENTRIPETAL FORCE
Centripetal force is the pull or force that keeps things moving in a
cricle. For example, gravity is the centripetal force acting on the moon.
Attach a fishing weight to a string and swing it around in a circle in
front of you. The string is the centripetal force acting on the weight.
Another idea is to fill a bucket with water and swing it quickly over
your head. The water will not come out because gravity is acting as the
centripetal force on the water.
BUOYANCY
Buoyancy is an upward force or upward thrust. For example, objects that
float in water are buoyant. Place fishing bobbers in a bucket of water,
try to press them down and they will pop right back up, this demonstrates
buoyancy. To see how things weigh less in water use a force gauge
calibrated in Newtons (Newtons are the unit of measuring force). First
measure the amount of newtons an apple weighs. Then put the apple in
water and measure the amount of newtons the apple weighs, this will
demonstrate liquid pressing against the apple causing it to weigh less.
FORCES IN BALANCE
Students should be made to understand that forces can be balanced. To
demonstrate this, have two students hold and pull the ends of a jump
rope. Then a third student pulls in the middle, this will show they will
balance out each others force.
INERTIA
Inertia is the tendency for objects to continue in their state of motion
or rest. This is in other words, Newton's first law of motion. This
explains why a passenger jerks forward when a car suddenly stops. To
demonstrate the effect of weight on inertia, tie a string to a rubber
band, place the rubber band around the bottom of a 2 liter plastic
bottle. Next pull on the string until the bottle starts to move.
Measure the amount that the rubber band stretches. Now fill the bottle
with water. Pull on the string until the bottle moves and again measure
the amount that the rubber band stretches. Results show that as weight
increases, inertia increases.
To demonstrate that an object continues to move due to inertia, stack
five books of about the same size on the edge of a chair or cart with
rollers. Push the chair or cart forward then quickly stop the chair. A
moving object remains in motion until some force stops it. The books are
not attached to the chair or cart; therefore, when the chair or cart
stops, the books continue to move forward. They would continue to move
forward in the air until hitting some other object except that the force
of gravity pulls them down. Air molecules also are hitting against the
books, slowing their forward motion. To demonstrate how a moving object
that hits an object at rest will propel the still object in the direction
of the moving object, set up a track using two books or rulers, place one
marble in the middle of the track and flick a second marble at the first
one and record what happens. Try using marbles of the same weight,
different weight, and you may also vary the amount of marbles you use at
one time.
FRICTION
Friction is a force that tends to slow things down or keep things from
moving. This force is found between things that touch. For example,
when an airplane touches the runway, the contact between the two slows
the airplane. Try removing a fairly tight
cover from a jar or thermos bottle with dry hands and with soapy hands.
Why must we be careful of water on a floor? Why do accidents sometimes
happen when people are in bathtubs? Friction is often used to " hold"
things.
Rough surfaces increase friction, therefore the greater the force used to
push an object, the greater the force due to friction. Another activity
that demonstrates how weight affects friction, take two of the same
toothpaste boxes. Empty one and leave the other full. Exert the same
force on both boxes and see which one moved
farther. Students can fill the boxes with different objects of different
weight and record what effec the weight has on the friction between the
box and the surface it is on.
Grease and oil are two examples that reduce friction. Their purpose is
to make surfaces slippery. For example, friction causes door hinges to
stick, when you add oil to the hinges the door opens easily. Wheels also
reduce friction because there is less area touching between the wheels
and the ground. To explain how friction can be reduced stack two large
books on a table. Tie a string around the bottom book, attach the string
to the rubber band and move the stack of books by pulling on the rubber
band. Measure how far the rubber band stretches. Now place 10 marking
pens under the stack of books. Move the books by pulling on the rubber
band, record how far the rubber band stretches now. This shows that
things that roll cause less friction than things that slide. Thus, there
is less friction between pens and the table than between the book and the
table.
SIMPLE MACHINES
Simple machines make work easier. The four common simple machines are
levers, a bar that moves things for example, a bottle opener or a
screwdriver. An inclined plane is a slanted surface. Types of inclined
planes include ramps, stariways, screws and a wedge. A pulley is a wheel
with a groove along its rim, a rope or chain fits into the groove.
Lastly the wheel & axle or (gears) are used to increase speed and
distance.
One activity that combines all ideas under the topic Motion & Force that
can be used in first and second grades is called Rolling Along, while in
third grade and up the Downhill Racer can be used. The Downhill Racer is
just an expanded version of Rolling Along. A group of students
experiment with an incline and a toycar. At three different heights of
the incline the car is let go from the exace place each trial. After the
car stops, the chidlren record and measure the distance from the bottom
edge of the incline to the rear wheels of the car. Each height should
have three trials, to help reduce experimental error. [Rolling Along and
Downhill Racer were developed by the TIMS Project and can be found in
the Math Trailblazers textbook series (Kendall Hunt).]
Some assessment ideas for this topic are (1) as the students perform the
experiments in groups they will be recording what they do, what happens,
controlling variables, influences outside the experiment that may affect
the resutls, and condition which they change and why and what affect the
changes has on the experiment. When they are done they will combine all
the results, discuss the results, draw conclusions, and record their
conclusions. Their notes will be included in their final report along
with their conslusion and explanation about why they reached this
conclusion.
The students will answer questions such as, "What other forces can you
think of and what effect do these forces have on objects?" This will
indicate to the teacher if the students have enough of an understanding
about the experiments they performed also to
be able to transfer this information to other areas.
Worksheets may also be used in order to help the teacher see how well the
students know the information and what areas need to be repeated. The
students woruld keep record books of their own in which they would record
what they did, their results, their prior knowledge, and what they
learned from each experiment. Portfolios can also be kept to enable the
teacher to see the progress of each student.
A list of resources that can be used with the topic Motion &
Forces include:
Benchmarks for Science Literacy
National Science Education Standards
Addison-Wesley Science: Addison-Wesley Publishing Company
Funk & Wagnalls Standard Reference Encyclopedia: Standard
Reference Works Publishing Company Inc. NY
Friction All Around by Tillie S. Pine and Joseph Levine
Gravity All Around by Tillie S. Pine and Joseph Levine
Simple Science Experiments with Marbles by Eiji Orli and Masako
Orii
Making Things Move by Franklin Watts
Gravity by Melvin Berger
The Science Book of Gravity by Neil Ardley
What Makes Things Move? By Althea
Forces in Action By Kathryn Whyman: This book goes through the
forces in the world in very simple and easy
terms that children can read understand.
Physics for Kids by Robert W. Wood:
This book easily illustrates 49 easy experiments with mechanics.
Simple Science Experiments with Starting and Stopping by Eiji and
Masako Orii: Great for the youngest children (K-2).
Push!Pull!Stop!Go! by RJ Lefkowitz: A simply explained book
about forces and motion.
I can be a Physicist by Paul P. Sipiera:
A great story book about what a physicist is and does.
Friction by Ed Catherall:
A dictionary type book about friction.
Mr. Grumpy's Motor Car by John Burningham:
An automobile ride turns into a muddy experience when a sudden shower
catches Mr. Grumpy and his friends in the middle of the fields.
Unfortunately, no one wants to be the one to help get the car unstuck,
but the animals learn that cooperation helps them solve the problem.
Choo Choo by Virginia Lee Burton: Choo Choo, the little steam
engine, was very tired of pulling a long line of passenger cars. One day
she took off alone, over the hills, through the cities, and into the
country where she ran out of steam. Choo Choo was rescued by the
streamliner and returned home, happy to be back with those who loved
her.
Mike Mulligan and His Steam Shovel by Virginia Lee Burton:
Mike, the enthusiastic steam shovel operator, symbolizes integrity,
determination, and hard work. Mary Ann, his well-loved steam shovel,
helps carry out any job Mike believes they can accomplish. Undaunted by
the threat of more advanced machines, Mike
and Mary Ann Meet the challenge of digging the cellar for the Popperville
town hall in a single day.
Mr. Gumpy's Outing by John Burningham:
A boat trip with Mr. Gumpy and his friends turns upside down. Now it is
up to everyone to find out how and who made the boat tip over.
Force and Motion by Peter Lafferty:
A resource book that encourages children to observe and question the
world around them.
Muscles to Machinesby Neil Ardley:
A book about movement. Explains the different ways things can move, and
describes the forces that work to slow down movement.
Make It Go by David Evans and Claudette Williams: A science book
designed for young readers. This book encourages children
to investigate their world through simple experiments-enabling them to
make their own scientific discoveries.
Gravity is a Mystery by Franklyn Branley: Explains in simple
text and illustrations what is known about the force
of gravity.
Force & Strength by Neil Ardley:
A science book that explains the basic principles of force and strength
through a balance of practical activities and information. The
experiments are fun to do, and can be performed by children on their own
or in groups.
The Science Book of Magnets by Neil Ardley: Simple experiments
that demonstrate basic principles of magnetism that
can be applied to the world around us.
Why Doesn't the Earth Fall Up by Bicki Cobb:
Answers nine questions about motion, explaining Newton's Laws of Motion;
gravity; centripetal force; and other principles of movement.
Magnets by Janice Van Cleave:
A collection of science projects and experiments using magnets.
Super Motion by Philip Watson:
A collection of information and exciting experiments about motion.
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