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Newton’s Three Laws
Last year we learned about Isaac Newton and all the
different things he invented and discovered. This year we
will be learning about his three laws of motion. We learned
about the first one last year, but we didn’t name it. His first
law of motion is called the Law of Inertia. It states that
objects in motion tend to stay in motion unless acted on by
an unbalanced force. It also states that an object at rest will
stay at rest unless act on by an unbalanced force.
When we played with the toy car and penny we observed
the penny continue moving when the car stopped. Let’s do
the same activity but change some variables.
Materials: Toy car, penny, 3 books same height, small
book, ramp, meter stick or ruler
What To Do:
1. Set up your ramp to look like the picture except use only
one book for the height of the ramp.
2. Place the small book at the end of the ramp to stop the
car.
3. Place the penny on top of the car and let it roll down the
ramp.
4. Use the ruler or meter stick to measure how far the penny
goes from the end of the ramp.
5. Add another book and repeat.
6. Add a third book and repeat.
7. Record your measurements in the data table.
Number of Books
Distance Penny
Traveled in cm
1
2
3
Questions:
1. In this activity we changed the number of books
that were under the ramp. How did this change the
motion of the car? ________________________
2. What happened to the penny? _____________
Watch the animation called Car and the Wall from
the website
http://www.physicsclassroom.com/mmedia/newtla
ws/cci.cfm
Then watch the Inertia video from
www.missdoctorbailer.com.
On the lines below write 3 sentences telling why
Newton’s Law of Inertia means we need to wear
seatbelts in a car.
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
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Newton’s second law is commonly known as
F=ma where F is the force in Newtons, “m” is the mass in
kilograms and “a” is acceleration. So, the Force need to
move an object can be calculated by multiplying the Mass
times the Acceleration you want the object to have.
An easy way to think about this is if you wanted to kick a
goal with a soccer ball or with a bowling ball. To make the
bowling ball move fast you would have to kick it much
harder than the soccer ball. Let’s see what happens when
we add mass to one of our cars.
Materials: two like cars, 50 g mass, masking tape, ruler,
ramp, three books.
What To Do:
1. Set up your ramp and 3 books as in the previous activity.
Do not put a small book at the bottom of the ramp.
2. Measure 30 cm from the bottom of the ramp and place a
piece of masking tape on the table like a finish line on a
racetrack.
3. Notice that one car has the 50 g mass taped to it.
4. Place both cars at the top of the ramp with the ruler
acting as a starting gate.
5. Lift the ruler so that the cars start down the ramp
together.
6. Observe which car crosses the finish line first. Do this
two more times for a total of three times.
7. Place a check mark in the data table below for the car the
crosses the finish line first.
Car
With mass
Without mass
Trial 1
Watch the video F=ma from
www.missdoctorbailer.com
Trial 2
Trial 3
We can use the formula F= ma to calculate the
forces on an object. Remember the unit for
force is the Newton.
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1. A train’s mass is 50kg and its acceleration is 5 m/s.
What is the net force on the train? __________
2. A car’s mass is 500 kg and its acceleration is 20 m/s.
What is the net force on the object? ______________
What if we wanted to know the acceleration? We can
rearrange the formula like you do in math.
F=ma can change to F = a
m
3. A bowling ball has a mass of 40kg and is kicked
with a force of 10 N. What is its acceleration? ______
4. A soccer ball has a mass of 10 kg and is kicked with
a force of 10 N. What is its acceleration? __________
What if we wanted to know the mass? We can
rearrange the formula like you do in math.
F= ma can change to F = m
a
5. A soccer ball is kicked with a force of 20N and
accelerates at 2m/s2. What is its mass?
6. A bowling ball is kicked with a force of 50N and
accelerates at 1 m/s2. What is its mass? __________
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The third law of motion states that for every action there is
an equal and opposite reaction. It is called the Law of
Action-Reaction. When you sit in a chair you push down
on the chair and the chair pushes back on you. This is
action-reaction. If you were at the Galleria, with your
friends at the ice skating rink and you pushed your friend’s
shoulder, your friend’s shoulder will push back on you.
Labe
l each action and reaction in the picture above.
Let’s try it with 2 skateboards.
Materials: 2 skateboard, 2 student volunteers
What To Do:
1. Two student volunteers will each stand on a skateboard
both facing the same direction.
2. The student in back with GENTLY push the other
student.
3. Observe what happens to both students.
4. Draw it below. Label the action and the reaction.
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Rockets are able to blast off because of Newton’s third
law. The rocket carries “propellants” which are
basically things that explode when you mix them
together and ignite them. The gasses from the
controlled explosions are forced out of the rear of the
rocket. The rocket pushes the gases out at a really high
speed. The gases push back and the rocket accelerates.
Because rockets push on these gases instead of pushing
on air they don’t need air molecules and can cruise
along just fine in outer space.
Materials: vinegar, baking soda, water bottle, beaker
with measurements, medicine cup with measurements,
tissue, spoon, rocket pattern, index card, cork, paper
clip, tape
What To Do:
1. Use the medicine cup to measure 2 ounces of baking
soda.
2. Place it in the tissue and roll it up to a size that will
fit into the water bottle opening. But don’t put it in the
bottle yet.
3. Place 100 mL of vinegar in the water bottle.
4. Use the rocket pattern to trace a rocket on the index
card.
5. Unbend the paper clip one time and push it into the
cork. Tape the rocket pattern to the paper clip. )See
picture on next page.)
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6. Go outside with your teacher.
7. One group at a time will launch their rocket by
putting the baking soda packet into the bottle and
putting the cork firmly into the bottle.
8. For safety everyone will stand back from the
launch pad and watch.
9. After each group has launched their rocket
gather up all materials and return to the classroom.
Summing Up
1. What is Newton’s 1st Law called? ______________
____________________________________________
2. What does it state? _________________________
____________________________________________
3. What is an example of it in our lives? ___________
____________________________________________
Questions:
1. What happened inside the water bottle? __________
____________________________________________
2. What did the mixing of baking soda and vinegar
produce? ____________________________________
3. How did this help the rocket launch? ___________
___________________________________________
4. The gas from the baking soda and vinegar pushed on the
rocket and the rocket pushed back. Which had the stronger
4. What is Newton’s 2nd Law called? ______________
____________________________________________
5. What does it state? _________________________
____________________________________________
6. What is an example of it in our lives? ___________
____________________________________________
force? ______________________________________
5. What was the action? __________________________
7. What is Newton’s 3rd Law called? ______________
6. What was the reaction? ________________________
____________________________________________
7. What kind of force caused the rocket to launch?
8. What does it state? _________________________
____________________________________________
____________________________________________
9. What is an example of it in our lives? ___________
Watch the Action-Reaction video from
www.missdoctorbailer.com.
____________________________________________
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Name __________________
period ____
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Name __________________
period ____
Exit Ticket
Exit Ticket
Newton’s Three
1. In a series of controlled experiments, a student measures
the force acting on a car and the car’s acceleration. The
student’s data are shown below.
Newton’s Three
1. A student argued that she would not slide backward
on here roller skates when she pushed her little sister
on her roller skates. Which of Newton’s laws is she
defying?__________________________________
2. In a series of controlled experiments, a student
measures the force acting on a car and the car’s
acceleration. The student’s data are shown below.
Based on the recorded observations and Newton’s 2nd law
(F=ma) what is the mass of the cart in kilograms?
________________________
2. A student argued that he did not have to wear a seatbelt
in the car because he was strong enough to stop himself
from flying out of the car if it stopped suddenly. Which of
Newton’s laws is he defying?
Based on the recorded observations and Newton’s 2nd
law (F=ma) what is the mass of the cart in kilograms?
________________________________________
3. A student argued that he did not have to wear a
seatbelt in the car because he was strong enough to
stop himself from flying out of the car if it stopped
suddenly. Which of Newton’s laws is he defying?
3. A student argued that she would not slide backward on
here roller skates when she pushed her little sister on her
roller skates. Which of Newton’s laws is she defying?
________________________
________________________________________
_________________________________________