Download Lab #14: Sudden Stops Hurt-Newton`s First Law

Lab #14: Sudden Stops Hurt-Newton’s First Law
In this lab, you will perform experiments about inertia and Newton’s First Law in terms of car crashes.
Objectives
You will:
 Describe situations with zero acceleration, other than objects at rest.
 Be able to explain the role of Newton’s first law and inertia in car crashes.
 Be able to explain the importance of seat belts in terms of physics concepts.
Background
Newton’s first law describes the motion and acceleration of objects. There are two parts to the
law. The first part says that an object at rest will stay at rest. The second part says that an
object in motion will stay in motion. Both parts of the law have an addition that say “unless acted upon by an unbalanced force.”
Tying together what we have learned so far about velocity and acceleration, look at the diagram to the right. Another way of
looking at this law is to say that objects will not accelerate unless they are acted on by unbalanced forces.
Pre-Lab Questions
1.
Can an object in motion have an acceleration of zero? If so, how?
2.
In a car crash, there are two collisions. The first one is when the car runs into the other car. What do you think the "second
collision" is? (Hint: It's the one that hurts)
3.
Refer to the picture to the right. The car is about to run into the wall. Make a
prediction about what will happen to the car, and what will happen to the person
in the car. PREDICTION: The car will _______________________, and the person in the car will _________________________.
Wooden Board
Setup:
Book (This is the "wall")
You will make observations to test your
prediction from above. Set up a ramp
and a "wall" as shown:
Book
s
Procedure:
1. Place a penny on the top of a toy car, and place the car's front wheels directly behind the 10 cm line.
2. Let the car go. Record the distance the penny flies from the cart. (If the penny is hitting the book “wall”, adjust the height of the
wall so that the penny can fly freely from the car). Repeat two more times from 10 cm.
3. Repeat steps 1-2 from 20 cm, 30cm, and 40cm, and calculate averages for these four distances. Graph your findings.
4. Using your graph, make a prediction about how far the cube will fly if the car is released from 55cm. Record in the table below.
5. Release the car from 55 cm and record the actual distance in the table below.
Data
Distance Up
Ramp (cm)
Distance Penny is Thrown (cm)
Trial 1
Trial 2
Trial 3
Average
distance (cm)
Qualitative Observations
10
20
30
40
55**
Distance prediction from graph: ___________
Actual distance from trial: _________________
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 1
Questions (separate piece of paper, please!)
1. Was your prediction about the car in the cartoon verified (proven true) by your experiments? Explain.
2. This lab involves the part of Newton’s First Law that says an object in motion will stay in motion unless acted upon by an
unbalanced force. Two objects are in motion in this lab. What are they?
3. What is the unbalanced force acting in this lab?
4. What object stays in motion, though the other object has been stopped by the unbalanced force?
5. When the penny is on the car, it travels in the same direction as the cart. When the penny is thrown from the car, in what
direction does it go? Why does the penny go in that direction?
6. Explain how seat belts work in terms of Newton’s first law and use the words “inertia” and “unbalanced force” in your answer.
Lab #15: Whiplash or Broken Nose-Newton’s 1st Law
In this lab, you will simulate several car collisions and make predictions about which direction the
“passengers” (metal cubes) in each will move.
Background
To summarize, Newton’s first law says that an object at rest will stay at rest, and an object in motion will stay in motion unless acted
upon by an unbalanced force. In Lab #14, you found that objects in motion (the car and the “passenger”), continue in motion, unless
acted upon by an unbalanced force (the book). The car is acted on by the unbalanced force, but the passenger is not, which is why it
continues moving forward. The passenger in the car is said to have inertia, which is a tendency for an object to do what it is already
doing. Many times, Newton’s first law can be summarized with just this one word: inertia.
Pre-lab Question
Observe the demonstration with the hard-boiled and raw egg. Explain what you see in terms of inertia.
Procedure
Front of Carts
1. Set up your ramp as it was in lab #14, minus the
books
at the bottom. You will be using dynamics carts
and
cubes as passengers in this lab.
2. Put one cart at the base of the ramp, 20 cm
from the ramp, as shown in the diagram below.
The front of the car should be facing away from
Back of carts
the ramp. Place a metal cube on that cart. This is the resting car.
3. Put the other cart on the ramp at the 20 cm mark, and put one
20 cm
cube in the middle of that cart. This is the crashing car. The front
of this cart should be facing toward the bottom of the ramp.
4. You should now have the resting cart set up to be rear-ended by the crashing cart. Let the crashing cart go and record what
direction the pennies on both carts move.
Prediction:
Using knowledge gained in lab #14, predict which direction you expect the pennies on each car to go. Refer to
specific directions like “toward the ramp” and “away from the ramp.” The penny on the resting car will _____________________
_________________________, and the penny on the crashing car will__________________________________________________.
Data
Trial Number
Direction of Motion of Resting Cart's
Penny
Direction of Motion of Crashing Cart's
Penny
1
2
3
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 2
Questions (on a separate piece of paper):
1.
2.
3.
4.
5.
Was your prediction verified? Explain.
If the penny on the resting cart had been the driver of a car that was rear-ended, would the
driver have more likely suffered whiplash or a broken nose? (Whiplash is when your head snaps
backward).
If you were a passenger standing in the aisle of a bus that suddenly lurched forward, how would
your body react? Why?
To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and
thrust downward at high speeds and stopped suddenly. Explain why this is done using the
following terms: inertia, unbalanced force.
The truck pictured to the right has a sturdy wall behind the driver's cab. What is the purpose of
this wall? Explain in terms of Newton’s First Law.
Lab #16: Newton’s 2nd Law: Calculating Force
Objectives:
You will:
 Measure the theoretical force of a rubber band Hot Wheels launcher directly by using a force meter.
 Calculate the actual force of a rubber band Hot Wheels launcher indirectly through calculation.
Background:
Newton’s second law describes how force, mass, and acceleration are related. First, this law states that if you do place a force on an
object, it will accelerate, i.e., change its velocity, and it will change its velocity in the direction of the force. It accelerates in the
direction that you push it.
Secondly, this acceleration is directly proportional to the force. For example, if you are pushing on an object, causing it to accelerate,
and then you push, say, three times harder, the acceleration will be three times greater. If you push twice as hard, it accelerates
twice as much.
Thirdly, this acceleration is inversely proportional to the mass of the object. For example, if you are pushing equally on two objects,
and one of the objects has five times more mass than the other, it will accelerate at one fifth the acceleration of the other. If it gets
twice the mass, it accelerates half as much.
Pre-lab Question:
Complete the following table, after reading the background above:
1.
2.
3.
4.
5.
Net Force
(N)
10
20
20
Mass
(kg)
2
2
4
2
10
Acceleration
(m/s/s)
5
10
Procedure: Direct Measurement of Force
1. Open the file “16-Newton2Law” from the App$ server in the Science/Logger Pro folder.
2. Attach the force sensor to the rubber band on the launcher, and pull it back to the first line on the board. Hold it as steady as you
can, and have someone record the force from the force meter in Logger Pro.
Force measured from force meter: _______________
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 3
Procedure: Indirect Measurement of Force
1. Take a Hot Wheels car and practice releasing it with the rubber band launcher. If the launcher seems to not be hitting the car
squarely or consistently, attach card stock to the back of the car to make a more consistent surface for the launcher to hit. Make
sure the card stock does not rub against the tires or otherwise negatively affect the movement of the car.
2. Measure and record the mass of the car in grams in the table below. Convert that mass to kilograms.
3. Click collect on Logger pro, and pull the binder clip with rubber band back to the first screw. Let the car go, and allow Logger Pro
to calculate the acceleration from the two photogates. Record the acceleration in the table below.
4. Calculate the Force in Newtons of the rubber band launcher (see the formula above).
5. Repeat steps 2-3 two more times.
Trial #
Mass of Car (g)
Mass of Car (kg)
Acceleration from Gate One to Gate Two
(m/s/s)
Calculated Force (N)
1
2
3
Average force (N):
Questions (on a separate piece of paper, please!)
1. The direct and indirect measurements of force were different. Brainstorm and explain 2 reasons why this might be.
2. If you were to double the mass of the car, how would you expect its acceleration to change?
3. If you were to double the mass of the car, how would you expect the force of the launcher to change?
Lab #17: Newton’s 2nd Law: Relationship between mass & acceleration
Objectives:
You will:
 Describe the relationship between mass and acceleration, when the force is kept constant.
Pre-Lab Questions:
Manipulated variable: ___________________________
Responding variable: ______________________
Controlled variables (2): ___________________________________________________________________
Hypothesis: If ___________________________________________________________________________________________, then
____________________________________________________________________________________________________, because
___________________________________________________________________________________________________________.
Procedure:
The Effect of Mass on the Acceleration of a Toy Car
Acceleration
Make a prediction about what the graph to the left will look like (sketch the shape of
the graph as a prediction):
1. Open the file “17-Newton2Law” from the App$ server in the Science/Logger Pro
folder.
2. Measure and record the mass of a car in grams. Convert that mass to kilograms.
3. Put the car in the launcher with the clip pulled back to the first screw, and make
sure the car is blocking the first photogate (red light should be on). Click collect on
Logger Pro, and let the car go. Record the acceleration in the table below.
Mass of Car
4. Repeat steps 2-3 two more times, being sure to pull the rubber band back to the
same screw each time.
5. Add 2 pennies to the top of the car and secure them with tape. Repeat steps 2-4. Continue adding 2 pennies until you reach 10
pennies. Calculate the average acceleration for each mass.
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 4
Mass of car
(g)
Mass of car
(kg)
Trial #
Acceleration from Gate One to Gate
Two (m/s/s)
Average Acceleration (m/s/s)
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Questions (answer on a separate piece of paper, please!)
1. Go back to your graph prediction. Roughly plot your data points from the table above onto that graph. Was your prediction
correct?
2. Describe the relationship between mass and acceleration of a toy car. Is it direct, inverse, or neither? Explain.
3. If you were to double the mass of your car, what would you expect to happen to the acceleration?
4. If you were to half the mass of your car, what would you expect to happen to the acceleration?
5. Write a conclusion for this lab.
Lab #18: Newton’s 2nd Law: Relationship between force & acceleration
Objectives:
You will
 Explain the relationship between acceleration and force, if mass is kept constant
Procedure:
1. Open the file “18-Newton2Law” from the App$ server in the Science/Logger Pro folder.
2. Measure and record the mass of a car in grams in the table below. Convert that mass to kilograms.
3. Click collect on Logger pro, and pull the binder clip with rubber band back to the first screw. Let the car go, and allow Logger Pro
to calculate the acceleration from the two photogates. Record the acceleration and force in the table below.
4. Repeat steps 2-3 two more times.
5. Pull the rubber band back to the second screw and then the third screw, and repeat steps 3-4 three times.
nd
6. Calculate the force at each point using Newton’s 2 law formula.
7. Print your graph.
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 5
Data:
Mass of car (g):
Force of
Launcher (N)
Trial #
Mass of car (kg):
Acceleration from Gate One to Gate Two
(m/s/s)
Average Acceleration (m/s/s)
1
2
3
1
2
3
1
2
3
Questions (on a separate piece of paper, please!)
1. Describe the relationship between force and acceleration of a toy car. Is it direct, inverse, or neither? Explain.
2. If you were to double the force acting on your car, what would you expect to happen to the acceleration?
3. If you were to half the force of your car, what would you expect to happen to the acceleration?
Lab #19:Newton’s 3rd Law: I Should’ve Seen it Coming!
Newton’s 3rd law states that for every action there is an equal and opposite reaction. While this is easy to
repeat and memorize, it isn’t so easy to understand and believe. For example, this means that when you push against a table, the
table pushes back on you with the same amount of force. (Think about that…it is easy to recite, but harder to understand). In this
lab, you will begin to investigate Newton’s 3rd Law by creating single-car accidents by running a dynamics cart into a wall.
Procedure: Part 1
1. Place the ramp 50 cm from a wall. Roll a car down the plane, releasing it from the 30 cm mark each time.
2. Measure and record the distance the car bounces. Move the ramp out of the way if necessary to allow the cart to roll freely after
hitting the wall.
3. Repeat steps 1-2 two more times.
4. Repeat the experiment 5 times, adding 50 grams of mass to the cart each time. Calculate the average distance for each test.
Pre-Lab Questions
Manipulated variable: ___________________________
Responding variable: ______________________
Controlled variables (2): ___________________________________________________________________
Hypothesis: If ___________________________________________________________________________________________, then
____________________________________________________________________________________________________, because
___________________________________________________________________________________________________________.
Grams on Car
Trial 1
Car’s Distance (cm)
Trial 2
Trial 3
Average Car distance
(cm)
0
50
100
150
200
250
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 6
Questions
1. Newton’s 3rd Law states that for every action, there is an equal and opposite reaction. What is the “action” in this lab? What is
the “equal and opposite reaction?”
2. Do you agree that the resulting action was “equal”? Explain how you came to this conclusion.
3. Do you agree that the resulting action was “opposite? Explain how you came to this conclusion.
4. Graph your results from this lab. It should be a line graph with “grams on car” on the x-axis and “distance traveled” on the yaxis. Be sure to label your graphs appropriately. (I have graph paper if you need it).
Lab #20:Newton’s 3rd Law: Man, that’s gotta hurt!
In this lab, you will continue to investigate this relationship, by creating car collisions. You should be
interested in observing what happens to the ramp cart, rather than the cart that is being run into.
Procedure: Part 1: Change in ramp cart’s mass
1.
2.
3.
4.
Place one cart 60 cm from the end of the ramp, facing away from the ramp. Place the other cart at the 40 cm mark of the
ramp so that it will hit the first cart when you let go.
Let go, and make sure at least one person is watching to observe the exact point of impact, because you will need to make
some measurements from the point of impact. What happened to the ramp cart? Measure the distance each car moved
from the point of impact and the direction of movement. Record your observations in the data table.
Repeat steps 1 and 2 two more times.
Repeat steps 1-3, each time adding 50 grams to the ramp cart. Stop when you reach 250 grams.
Pre-Lab Questions
I expect the ramp cart to move in the following direction (describe):_____________________________________________________
This is what I expect to see in the distance traveled by the ramp cart as I add more weight:_________________________________
I expect the resting car to move in the following direction (describe): ________________________________________________
This is what I expect to see in the distance traveled by the resting cart as I add more weight to the ramp car:
__________________________________________________________________________________________
What is the manipulated variable? _________________________
Ramp Cart Mass
(g)
0
Ramp Cart’s Direction (away
from or toward point of impact)
Ramp Cart’s
Distance (cm)
Resting Cart’s Direction (away from
or toward point of impact)
Resting Cart’s
Distance (cm)
50
100
150
200
250
Procedure: Part 2 (Change in resting cart’s mass)
5.
Now, remove the weights from the ramp cart and add them one at a time to the cart at the bottom of the ramp following
the same procedure above. Again, record your observations and measurements.
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 7
Grams on Resting
Car
0
Ramp Car’s Direction
Ramp Car’s
Distance (cm)
Resting Car’s Direction
Resting Car’s
Distance (cm)
50
100
150
200
250
Questions
1. Newton’s 3rd Law states that for every action, there is an equal and opposite reaction. What is the “action” in this lab?
__________________What is the “equal and opposite reaction?” _____________________________
2. Do you agree that the resulting action was “equal”? Explain how you came to this conclusion.
3. Do you agree that the resulting action was “opposite? Explain how you came to this conclusion.
4. Graph your results from both labs. The first graph should be a double line graph with “mass on cart” on the x-axis and “distance
traveled” on the y-axis. You will have one line showing the ramp car’s data, and one showing the resting car’s data. Your second
graph should be a double line graph.
Lab #21:Newton’s 3rd Law: Tug of War
In this lab, you will continue to investigate Newton’s 3rd Law by playing a small rubber band tug of war at your
lab station.
Procedure
1.
2.
3.
4.
Make sure that you have 2 force sensors plugged into the Lab Pro box. Click collect and push and pull gently on the hooks for
the force sensor. Get a sense for which sensor gives which color on the graph, and what causes positive and negative graphs.
Attach a rubber band to the hook of each force
sensor.
Prediction: Put the force sensor down and consider
the following situation: Suppose that 2 force sensors
were connected to a single rubber band. If one
person pulled their force sensor while the other
person simply stood still, what would the resulting
graph look like? Pretend that the graph to the right
shows what the puller’s graph will look like. What
will the other person’s graph look like? Sketch it on
this graph.
Connect both force sensors to a single rubber
band. Make sure the rubber band has no tension
on it. Click “Collect” and have one person pull and
the other person stay still. Sketch the resulting
graph to the right.
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 8
5. Reverse roles: the puller becomes a holder and the
holder becomes a puller. No need to switch sensors.
Record your graph to the right.
6. Have both people pull. Record your graph to the right.
7. Attach one force sensor to a ring stand as shown.
Connect the other force sensor by rubber band to the
one on the ring stand. Have someone securely hold the
ring stand in place. Repeat the previous activity.
Questions
1. Complete the following statement and use the words
“magnitude” (size) and “direction” in your response.
Whenever one object exerts a force on a second object, the second exerts a force on the first that is:
2. So in a real tug-of-war, Newton’s 3rd Law says that as team one pulls on team two, that team two pulls back with an equal and
opposite force on the team one. Explain how this could be with writing and diagrams.
3. If #2 is true, how can anyone ever win at tug of war? Draw a stick figure that represents a tug of war participant. Complete a
force diagram for this person. What force allows a tug of war participant to win?
Ready to turn your packet in? You should have all questions completed in this packet (25 pts.). You should have attached to this
packet:
 Questions for labs 14-21 (25 pts.)
 Graphs that you made for labs 19-20 (10 pts.)
 Graph printed from lab 18 (5 pts.)
Reading in lab 14 taken from http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l1a.html, reading in lab 16 taken from
http://id.mind.net/~zona/mstm/physics/mechanics/forces/newton/newtonLaw2.html , lab 21 adapted from The Book of Phyz by Dean Baird , labs
19 and 20 Adapted from http://alex.state.al.us/lesson_view.php?id=6183
Page 9