Download File - Mr. Walsh

Name: ________________________________ Date: _______________ Period: _____________ ID: _______
Lab: How does inertia affect the motion of objects?
Purpose:
- To see how Newton’s First Law is shown through everyday objects.
- To see how inertia is present in different situations
Hypothesis:
Write a hypothesis in response to the title of the lab. Be sure to include your reasoning, which should
include a definition of inertia and any examples that you can provide to support your ideas.
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Procedure:
1. You will be moving around with a partner to the different stations throughout the room. At each station,
follow the instructions printed on the paper.
2. In each case, you will first generate a prediction or hypothesis. Make sure to briefly explain your
reasoning before you try to complete the given task!
3. Record your observations in an organized way. You may want to make drawings, an observations table
with a checklist, or any other method that will work for you.
4. Go to as many stations as possible in the time allowed. If needed, we can continue the observations on a
second day. Some stations take longer than others so please do not rush a group that is working slowly.
When possible, there are double set-ups, so wait your turn to get to an empty station.
Stations
1. Coin Karate: Can you remove the bottom coin from a tall stack without toppling the entire stack?
2. Magic Act: Can you pull the tablecloth out from under the settings without moving the dishes?
3. Eraser Drop: An eraser is balanced on a wooden hoop which is balanced on the mouth of a bottle. Can
you get the eraser to drop into the bottle by touching it only once?
4. Card Snap: Can you remove the card without moving the weight?
5. Mini-Hovercraft: How do objects move when friction is reduced to nearly zero?
6. Pile of Blocks: How can a block be inserted at the bottom of a pile without touching the pile itself?
7. Car Crash: What effect does a car crash have on a passenger not wearing their seatbelt?
8. Dizzy Chickens: Which egg is raw?
9. Hinged Stick: Is it possible to drop the ball into the cup on the stick?
10. Dime Drop: Can you have the dime end up inside of the bottle without picking up the card to slide in
the coin?
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
Station
Coin Karate
(Yellow)
Question
Can you remove the bottom coin from a
tall stack without toppling the entire
stack?
Magic Act
(Blue)
Can you pull the tablecloth out from
under the settings without moving the
dishes?
Eraser Drop
(Dark Purple)
An eraser is balanced on a wooden
hoop that is balanced on the mouth of a
bottle. Can you get the eraser to drop
into the bottle by touching it only once?
Card Snap
(Orange)
Can you remove the card without
moving the weight?
MiniHovercraft
(Lime Green)
How do objects move when friction is
reduced to nearly zero?
Pile of Blocks
(Light Purple)
How can a block be inserted at the
bottom of a pile without touching the
pile itself?
Car Crash
(Gray)
What will happen to the toy figure
when he crashes into the wall?
Dizzy
Chickens
(Salmon)
How can you tell which egg is raw?
Prediction
Observation
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
Is it possible to have the marble end up
Hinged Stick
(Pink)
in the cup on the stick?
Dime Drop
(Green)
Can you have the dime end up inside of
the bottle without picking up the card to
slide in the coin?
Analysis:
Discuss what each demonstration has to do with inertia or Newton’s First Law of Motion. You may have
noticed that some of the activities demonstrate similar concepts. You may find it easier to group the demos
by type and then discuss them.
1. Coin Karate:
2. Magic Act:
3. Eraser Drop:
4. Card Snap:
5. Mini-Hovercraft:
6. Pile of Blocks:
7. Car Crash:
8. Dizzy Chickens:
9. Hinged Stick:
10. Dime Drop:
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
Inertia Challenges Weebly Rubric
Section
Description
(Max. Points)
Basic Details Name(s) of Lab Partner(s) listed.
Date lab conducted listed.
(5)
Class period listed.
Points Earned
Purpose and
Hypothesis
(10)
Objective is related to the purpose of the experiment and states
what you want to prove/discover/illustrate from the experiment.
Hypothesis written as a possible explanation for the objective,
and is capable of being tested by the experiment. Includes
theories, laws, equations to be tested. (Hint: Newton’s 1st law of
motion)
ProcedureSketchDescription
(15)
A brief description of the experiment is included by the student.
A sketch of at least 5 different situations is included in the lab.
Sketch is labeled as appropriate station.
Also includes a video of one station being completed.
Data
Table
(15)
Analysis
(10)
Construction of an acceptable data table. Must be organized, neat
and descriptive.
Conclusion
(15)
Discusses hypothesis and sources of error in lab. Provides an
example of inertia in everyday life and states whether or not the
objective of the lab was complete by citing evidence conducted in
lab. (Use Conclusion Questions from Lab Write Up Guide)
Mechanics
(5)
No spelling errors. Uses complete sentences for responses.
Neat and organized in appearance.
Discusses in detail what each demonstration has to do with
Newton’s 1st law of motion.
Total Score:
____/75
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
Nickel Karate
Materials: Several nickels.
Procedure: Stack four to five nickels into a neat pile on a table. Use your finger to flick another nickel at the
stack of pennies hitting the bottom nickel. Attempt to have the nickel squarely hit the nickel on the bottom of
the stack. What do you think will happen? Why?
Conclusion
The bottom nickels will pop out of its place from under the stack. When this happens, the nickel that you flicked
will either stop or bounce back depending on how you flicked it. The nickel on the bottom of the pile has
'inertia at rest'. An explanation of this is: An object at rest stays at rest unless acted upon by an outside force.
The nickel you flicked has 'inertia of motion': an object in motion stays in motion unless acted upon by an
outside force. The moving nickel changes its inertia w/ the nickel on the bottom of the stack. Try it with other
coins and see what happens!
Toilet Paper Roll
If I pull slowly, it just keeps coming from the roll. To tear it, I have to give a quick jerk. Put TP roll on a short
pipe to hold it, and try pulling. That's inertia. It's defined by the first part of Isaac Newton's First Law, "An
object at rest tends to stay at rest." Newton goes on to add that "An object in motion tends to stay in motion."
We'll get to that later. A slow pull gives the TP roll time to get moving, and the paper comes off. But a quick
pull tears because the big roll tends to stay at rest and so resists the sudden force. This resistance is what we
mean by inertia. It's a fundamental property of mass. This explains one of those things we learn young, that it's
hard to tear the paper at the end of the roll. There's not much mass. so the paper runs out all over the floor
instead of tearing. Demonstrate pulling with a small roll of TP.
Coin and tumbler
Place the coin on the card, and place the card over the open end of a beaker.
Flick the card away sharply and observe the effect of the coin’s motion.
Pulling the card slowly means the coin has a low acceleration, and so the
frictional force between card and coin is big enough to accelerate the coin.
Pulling the card quickly requires too great a frictional force to accelerate the
coin and so slipping occurs.
String Pull
Two identical heavy steel balls with hooks on opposite sides are suspended from a
support by strings. It is important for the support to be quite rigid. A string dangles from
the bottom of each ball. The audience is told that all the strings are identical and asked to
vote on which string will break first if the lower string is pulled on one of the balls. If
the audience votes that the upper string will break first, one reaches over and gives the
string a jerk in order to make it break below the ball. While the spectators are puzzling
over why their intuition was wrong, one offers to repeat the experiment with the second
ball while commenting on the importance of repeating scientific experiments, but this time the string is pulled
very gently to make the string break above the ball. The audience is asked to explain why the result was
different. If the vote were the opposite, one would reverse the order of the demonstrations. The importance of
controlling all the relevant variables in an experiment can be discussed. A single ball can be used if one takes
the time to retie the string between each demonstration.
The explanation involves the inertia of the ball. With a quick jerk, the ball has to accelerate, and a considerable
force is required to do this if the mass of the ball is large (F = ma). On the other hand, with a slow pull, the
acceleration is negligible, and the upper string is supporting the weight of the ball plus the tension in the lower
string, causing the upper string to break. From Newton's second law, Tu - Tl = m(g-a) where Tu is the tension in
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
the upper string, Tl is the tension in the lower string, m is the mass of the ball, g is the acceleration due to
gravity (9.8 m/s2) and a is the downward acceleration of the ball. Thus the upper string breaks when the
downward acceleration of the ball is less than 9.8 m/s2; otherwise the lower string breaks.
Pile of books
Set up a pile of books or magazines on the bench and pull out one of the books in the
middle quickly.
Horizontal snap
Show that the thread can support a suspended mass of
thread to the small mass. Hold the other end of the thread
Step h: For strong sewing cotton you will need a mass of
abrupt jerk of the thread will break it. A slow pull just
along, but a quick pull snaps the thread because the force
acceleration of the mass is greater than the thread's breaking strength.
about 100 g. Tie the
with the thread slack.
at least 5 g. A very
moves the mass
required for the high
Pile of blocks
Build a pile of four blocks. The blocks should be smooth blocks of wood, say
10 cm x 7.5 cm x 5 cm with their edges and corners rounded. Push a fifth brick
quickly at the bottom brick of the pile. The fifth brick goes in and the bottom
brick goes out. This is most dramatic if the fifth brick is projected along the
table towards the pile by hitting it with a small mallet. The only force that the
moving book can exert on the pile of books above it is friction. If the
acceleration of the moving books/blocks is large enough, there is insufficient force to make the pile above it
move too.
Inertia with two metal can pendula
Use long strings to suspend from the ceiling two large identical tin cans or buckets. Fill one can with sand. Use
the hook of a spring balance to push each can in turn. Note what force is necessary to start the cans moving. Use
your hand to stop the cans when they are moving. You can feel the difference in inertia of the two cans.
Mini-Hovercraft!
Supplies: Cardboard, Pencil, Glue, Paper, Thread Spool, Balloon
1. Cut a 4-inch square out of the cardboard.
2. Punch a hole in the center of the cardboard. The hole should be the same size as the hole in the spool.
3. Glue the spool to the cardboard on top of the hole. Make sure the holes line up. Make sure you use
enough glue to assure that no air can escape between the spool and the piece of cardboard. Make sure
you put the lid back on the glue when you're finished.
4. Cover the top of the spool with a circle of paper - glue it to the spool and wait until the glue is good and
dry.
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
5. Punch a hole in the middle of the paper cover where the hole of the spool is. Now your hole should run
through the paper, spool, and cardboard without any obstructions (watch for too much glue).
6. Blow up the balloon and twist the end to keep the air from escaping. Stretch the balloon over the top of
the spool.
7. Set the hovercraft on a level table. Let go of the balloon.
8. Give the hovercraft a few gentle pushes.
The air flowing from the balloon through the holes forms a layer of air between the hovercraft and the table.
This reduces the friction. This layer of air reduces the friction that would have existed if the hovercraft rested
directly on the table. With less friction, your hovercraft scoots across the table.
Rolling Chain
MATERIALS: small, flexible chain (about 60 cm long) wrapped into a loop, wooden disk to fit chain, electric
motor, wooden stick
PROCEDURE
A chain wrapped around a wooden cylinder and spun up to a large rotational velocity with an electric motor can
be nudged off the cylinder with a stick. The chain will retain its circular shape and will roll across the lecture
table and across objects in its path until eventually coming to rest in a pile on the floor some distance away. The
chain can be made to climb a ramp and fly across the room. A 20-cm-diameter cylinder rotating at 2500 rpm
makes an effective demonstration.
DISCUSSION
The chain retains its shape because of the inertia of each of its pieces which tend to move in a straight line
tangent to the circle. This tendency is often ascribed to an outward centrifugal force, but it is not a force at all.
In fact the force is a centripetal force acting toward the center of the circle in order to keep the chain from flying
apart. Alternately, one can describe the behavior of the chain in terms of the conservation of angular momentum
which requires it to continue rotating until sufficient frictional torque brings it to rest.
Beaker and Tablecloth
A glass beaker, partially filled with water, rests near the edge of a table on a cloth which is rapidly pulled out
from underneath the beaker without spilling the water or breaking the beaker.
MATERIALS: large glass beaker with smooth bottom and smooth cloth without
seam
PROCEDURE
The beaker is filled about two-thirds with water and placed on the cloth some
distance from the edge of the table. Make sure the cloth, table and beaker are
clean and completely dry. The table and the bottom of the beaker should be
smooth, and the cloth should not have a seam at the edge. Slowly pull the cloth
until the beaker is about 2 cm from the edge of the table and then quickly jerk the
cloth out from under the beaker. The beaker should remain on the table, and no
water should spill. As one gains confidence, the demonstration can be done with other objects such as an entire
table setting, but it's easiest if the objects have smooth bottom surfaces. A paper towel can be used instead of
the cloth.
DISCUSSION
According to Newton's first law, an object at rest tends to remain at rest until acted upon by an external force. In
this case, the external force is the friction force between the beaker and the moving cloth. The friction force has
a maximum value proportional to the mass of the beaker and its contents, F = µmg, where µ is the coefficient of
friction (typically a few tenths) and g is the acceleration due to gravity (9.8 m/s2). According to Newton's
second law, this force produces a maximum acceleration of a = F/m = µg. Thus if the cloth is pulled gently
(acceleration less than µg) the beaker accelerates along with it, but if the cloth is jerked suddenly (acceleration
greater than µg) the cloth is removed before the beaker can accelerate to a significant velocity. What small
velocity it does acquire is quickly brought to zero by the friction between the beaker and the table after the cloth
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
has been removed. An additional effect that contributes to the success of the demonstration is that the
coefficient of sliding friction is less than the coefficient of static friction. Note that the mass of the object
cancels, in contrast to popular misconception, so that it is no easier to perform the trick with a heavy object than
with a light one. This fact can be illustrated by repeating the demonstration with an empty beaker.
Boiled and Raw Eggs
Materials: Hard boiled egg, raw egg
Procedure: Spin the eggs, one at a time, on the side on a smooth hard surface, stop them fast and let them go
immediately. The boiled egg will spin easily to begin with but will not spin any more after stopped suddenly
and released. However, the raw egg will spin again after quick stopping and releasing it because the liquid
inside the raw egg is still in motion due to inertia.
Inertia of Air Molecules
Materials: 10-12 inch long, 1 inch wide, and 1 inch thick wooden stake, 16 inch by 16-17 inch sheet of paper
(two legal sheets of paper can be taped together, or a newspaper sheet), table
Procedure:
Spread the sheet of paper on the table aligning its edge with the edge of the table. Insert and center the stake
under the paper with less than half protruding out from the paper/table edge. Hit the stake fast with hand (like
karate chop) closest to the table without hitting tabletop. The stake will break if done correctly. Do not touch the
paper when stake is being hit. The paper surface is carrying an air pressure of 15 psi and when stake is hit, it
tries to accelerate the air above the paper surface which offers resistance enough to cause the stake to break.
The students should be moved a little far from the activity as the shattering wooden pieces can hit somebody
and might cause injury.
Big and Small Masses
Materials: 6-7 kg round or square mass with hooks on opposite ends, 0.5-0.6 kg round or square mass with hook
on one side, string (just strong enough to support the heavy mass), stand
Procedure:
Place the stand at raised level. Suspend the large mass from the stand using about 2 feet long string leaving
about one foot space between the mass bottom and the floor. Make sure that stand and the hanging mass are
stable and can withstand pulling of mass with a slight jerking action. Hang the smaller mass with 2-3 inch string
from the bottom hook of the bigger mass. Pull down the smaller mass with a slight jerking action. The smaller
mass would come off without affecting the bigger mass. The larger mass offers resistance when smaller mass is
pulled abruptly. It is an action similar to when paper towel or tissue paper is pulled out from a bigger roll with a
fast jerking action.
Square/Round Peg and Wooden Block
Materials: 10-12 inch long square or round wooden peg, wooden block (more massive than the peg) with a hole
just big enough for peg end to fit snugly, hammer
Procedure:
Lightly insert peg end into the block hole. Hold the peg and block assembly in hand and tap the open end with
hammer. With each tap the peg will move further into the hole of the block. The block does not have to be held
against any hard surface. Because of the mass of the block it resists motion when the peg is tapped down.
Inertia Balance
Description: The inertia balance is designed for use in a laboratory experiment in which mass is quantitatively
measured independent of the earth's gravitational force. This same method is used in determining the mass of an
object under weightless conditions in space flights. The apparatus consists of two small platforms connected by
two horizontal, nonsagging, spring-steel blades. A cylinder with a shoulder on which it can rest in a hole in the
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
platform and a hook by which it can be suspended are included. This cylinder may be used as an object of
unknown mass.
Materials: Inertia balance, 6-100 gram masses, Stopwatch, unknown mass
Instructions:
1. Securely clamp the inertia balance to a well-braced laboratory bench by means of a C-clamp. The
platform with the hole should be used for supporting the load.
2. Use a stopwatch to determine the time for a given number of
vibrations. Begin with a load of two 100 gram masses on the platform
and determine the time for 100 vibrations. By using small amplitudes
and waiting until several oscillations have occurred before timing,
there will be no slippage of the weights on the platform. Repeat,
determining the time for 100 vibrations for loads of 3, 4, 5 and 6
weights.
3. Compute the period in seconds for each load and plot period against
the weight of the corresponding load. Also, plot period squared against
the corresponding load. Which curve is more nearly a straight line, and what conclusion can be drawn as
to the relationship between mass and period?
4. Place the unknown mass in the hole of the platform and determine the period of the vibration. From the
calibration curve, obtain the mass of the unknown and compare the value with that obtained by weighing
the unknown on a balance.
Pen and Embroidery Hoop
Description: No matter the pen or bottle used, this demonstration of the inertia of
rest requires practice and knowledge of the trick (not really a trick) to have this
"in the bag" (or bottle...)
Instructions: Balance the hoop on the mouth of the bottle, and a pen (directly
above the bottle) on the hoop. Ask the students what they think will happen when
the hoop is removed, even have a student come up to prove it. They often will try
to push the hoop off the bottle by approaching it from outside of the hoop. This
will pop the pen up in the air, and it will most likely miss the target. The trick
mentioned above is to approach the hoop from inside the hoop. When you grab
the hoop from inside, the hoop compresses a bit, and the pen will have no initial
upward motion.
Coin and Plastic Ring
Instructions: Balance the ring on the mouth of the bottle, and a coin (directly above the bottle) on the ring. What
do you think will happen when the hoop is removed? Try striking the ring at different positions. Try rings of
varying rigidity. Which gives the most consistent effect?
Eggs and Pizza Pan
Materials: Three beakers with water, 3 plexi-glass cylinders, 3
golf balls or eggs, 1 pizza pan, 1 broom
Instructions: Place three beakers of water in a (roughly) triangle
shape on the bench relatively close together. Place the pizza pan on
top of the beakers, the cylinders on the pan (above the beakers!)
Name: ________________________________ Date: _______________ Period: _____________ ID: _______
and the eggs on top of the cylinders. Make sure this whole system is close to the edge of the bench, so the pan
hangs of the edge a bit.
Stand on the bristles of the broom, pull the handle back, and let go of the broom to allow the handle to hit the
edge of the pizza pan. With practice, the eggs will drop safely into the beakers of water. Broom side held on the
floor under foot and releasing handle at an angle to hit the board would provide a better impact. As the board
flies away the eggs would fall in water. As the metal plate is hit, the eggs just resting above it resist horizontal
motion and fall down under the influence of gravity.
Soda Straw Egg Drop
Materials : 10 Soda Straws, Cellophane Tape, Egg
Procedure: Construct an egg protection container using fewest number of soda straws and least amount of tape
(no other materials are allowed). The tape may NOT touch the surface of the egg, and the egg must be visible
and accessible at all times. Then, drop the container with the egg inside from the ceiling.
Card Snap
Place the index card on the stand, placing a weight on top of it. Pull back the leaf spring and note what happens.
Try other masses. Which give you the best effect, heavier or lighter masses?