Monday,
November 4, 2013
Physics
Standards: 1c Students know how to
apply F=ma to solve one-dimensional
motion problems that involve
constant forces.
Learning Objective: SWBAT create a
force meter to study gravity
Agenda:
1. Warm Up
2. Force Meter Lab
3. Gravity Discussion
4. Put a scale on the force meter.
Warm Up
A 200 kg piano falls from
the sky. How much does
the piano weigh?
Homework
#FH4
Tuesday,
November 5, 2013
Physics
Standards: 1c Students know how to
apply F=ma to solve one-dimensional
motion problems that involve
constant forces.
Warm Up
Find the net force of a 1kg
ball accelerating under a
55N Force, when friction is
16N and air resistance is 8N?
Learning Objective: SWBAT build a
force meter and use it to understand
how gravity works.
Agenda:
1. Warm Up
2. Review Test
3. Take Survey
4. Finish Lab
Homework
#F4
Wednesday,
November 6, 2013
Physics
Standards: Standards: 1c Students know
how to apply F=ma to solve onedimensional motion problems that involve
constant forces.
Warm Up
If a 1000kg car
accelerates at 5 m/s2,
what is the applied Force
of the car’s engine.
Learning Objective: SWBAT understand
how weight functions and build a a Force
meter.
Agenda:
1. Warm Up
2. Discuss Mousetrap Car Lab
3. Tell Students their grades
4. Finish Force Meter Lab
Homework
#F4
Thursday,
November 7, 2013
Physics
Warm Up
How much does 200g
weigh?
Standards: Standards: Standards: 1c
Students know how to apply F=ma to solve
one-dimensional motion problems that
involve constant forces.
Learning Objective: SWBAT : SWBAT
understand how weight functions and build
a a Force meter.
Agenda
1. Warm Up
2. Review Homework
3. Finish Force Meter
Homework
NA
Friday,
November 8, 2013
Physics
Standards: 1c Students know how to apply F=ma to
solve one-dimensional motion problems that
involve constant forces.
Learning Objective: SWBAT
Agenda:
1. Warm Up
2. Newton’s 3rd Law Tug of War Lab
1. Engage – Predict result of
pushing roller chairs
2. Explore- Predict Force Meter
Readings
3. Explain – N’s 3rd Law Mini
Lecture
4. Elaborate – Take Measurements
with Masses on the end of the
force meters.
5. Discuss Results
3. Evaluate#F5 Newton’s 3rd Law
Warm Up
a. If your Force Meter reads
9N when an object of
unknown mass hangs
from it, find the mass.
Homework
#F5 Newton’s 3rd Law
Symbols, units and
equations Study Guide
Equations:
Constant Velocity
v=
Dx
Dt
d
v
=
Dy = y f - yi s t
Dx = x f - xi
Constant Acceleration
a=
Dv
Dt
Dv = v f - vi Dy = y f - yi Dx = x f - xi
The Two equations of Motion
1.
2.
v f = vi + at
1
Dx = at 2
2
The Two equations of Motion
for Falling Objects
ag
=-9.8m/s2
v f = vi + agt
1
Dy = agt 2
--distance(d) and
displacement (Δx or Δy )
units: meters (m)
--speed (vs),
velocity (v) units: meters per second or
kilometers per hour (m/s, or km/hr)
--acceleration (a) units: meters per second
squared or kilometers per hour squared (m/s2,
km/hr2)
--time or change in time (t or Δt) units: seconds
Forces
Fnet = ma
Fg = W = mg
Fnet = F1 + F2 + F3 +...Fn
Fnetx = F1x + F2 x + F3x +...Fnx
Fnety = F1y + F2 y + F3y +...Fny
Force Meters
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Force Meters
Objective: Students construct rubber band force-meters to aid in the
investigation of forces and Newton’s 3rd Law. See Figure 5.
Engage
Watch Video:
Why do objects weigh less on the moon?
What else might affect the weight of an object?”
Explore
How can we use a rubber band to actually determine the weight (the
force due to gravity) of an object?
Explain
In order to actually put numbers on our force meters, we have to know
the formula for figuring put the amount of gravitational force Fg from a
certain amount of mass m.
The formula is Fg = mg (or W = mg)
Elaborate
How is this related to Newton’s 2nd Law, Fnet = ma?”
Evaluate
Students should now create an accurately labeled scale on their
force-meters, displaying the applied force in units of Newtons.
Problem Set: #F4 Fg = mg.
Figure 5. Rubber
band force-meter
Types of Forces
• From your book p. 94 Table 4-2
Force
Symbol
Definition
Direction
Friction
Ff
Resistive Force. Comes
from rubbing against or
sliding across surfaces.
Parallel to the surface and
opposite the direction of
sliding
Normal
FN
The force exerted on an
object by the ground, a
table, a platform, or any
surface.
Perpendicular to and away
from the surface.
Spring
Fsp
Restoring Force. The push
or pull a spring exerts on
an object.
Opposite the
displacements of the object
at the end of the spring.
Tension
FT
The pull exerted by a
string, rope, or cable when
attached to something.
Away from the object and
parallel to the string, rope,
or cable at the pont of
attachment.
Thrust, Applied Force
Fthrust,Fap
A general term for the
forces that move objects
such as rockets, planes,
cars and people.
In the same direction as
the acceleration of the
object.
Weight
Fg
Attractive Force of two
objects due to gravity.
Usually Earth and and
object
Straight down towards the
center of the earth.
Air Resistance/Drag
FAR
Resistive Force, comes
from air/wind hitting
moving objects
Opposite of Motion
Calculating Net Force
F1b
Directions: Combine (add and/or subtract) all the forces on each box to determine the net force. Then decide if
the forces are balanced or unbalanced and if the object is moving or stationary.
1.
2.
5N
5N
3.
3N
6N
2N
8N
5N
Net force =
Balanced or Unbalanced
Accelerating?
4.
9N
3N
Net force =
Balanced or Unbalanced
Accelerating?
5.
4N
Net force =
Balanced or Unbalanced
Accelerating?
6.
8N
6N
7N
6N
9N
7N
3N
Net force =
Balanced or Unbalanced
Accelerating?
7.
5N
2N
3N
8N
Net force =
Balanced or Unbalanced
Accelerating?
8.
4N
4N
4N
4N
5N
9N
7N
Net force =
Balanced or Unbalanced
Accelerating?
10.
5N
6N
6N
Net force =
Balanced or Unbalanced
Accelerating?
2N
6N
Net force =
Balanced or Unbalanced
Accelerating?
Net force =
Balanced or Unbalanced
Accelerating?
11.
12.
6N
2N
2N
8N
3N
6N
2N
6N
12N
Net force =
Balanced or Unbalanced
Accelerating?
9.
6N 6N
3N
11N
4N
4N
Net force =
Balanced or Unbalanced
Accelerating?
8N
8N
8N
8N
8N
4N
Net force =
Balanced or Unbalanced
Accelerating?
#F2
nd
2
Newton’s
Law
Problems
1. If a student accelerates on his/her bicycle at 4m/s2, and the student has
a mass of 77 kg. How much force does s/he apply to the bicycle?
2. Find the weight of the following people: Rickey is 100 kg, Manny is
150kg, and Donna is 65kg and the acceleration due to gravity is 9.8m/s2.
3 How much force does a baseball experience if the baseball bat
accelerates the ball at 8m/s2 and the mass of the baseball is 5kg?
4. How much force would a 10kg baseball experience if the bat
accelerated the ball at 20m/s2?
5. What is the mass of a bullet that accelerates at 100m/s2 by a 12 N Force
when shot out of a gun?
6a. Thrust from a rocket’s engine equal to 100,000 N launches a shuttle
with a mass of 10,000 kg into the air. What is the rockets acceleration?
6b*If the acceleration due to gravity is 9.8 m/s2 will the rocket be able to
escape the earths atmosphere?
7. A wide receiver (90 kg) is tackled after catching a football by one of the
safeties (99 kg). The safety applies a force of 250N? How fast did the
receiver decelerate? (Be careful when you choose which mass to use.)
Newton’s
nd
2
Law 2 #F3
1. What does Fnet mean?
2. What is the equation Newton’s 2nd Law.
3. What do you change from Newton’s 2nd Law equation
in order to find weight (W or Fg) ?
4. Find the net force of mini car racing if friction is 20N, the
accelerator supplies 50N, and air resistance is slowing it
down by 2N.
5. If the car from problem 4 has a mass of 1 kg, what is the
car’s acceleration?
6. Which direction does Gravitational Force push?
7. Describe the Normal Force?
8. Friction acts in which direction?
9. If an object is flying northeast, which direction is air
resistance pushing?
10. Find the mass of an object if it accelerates at 2 m/s2,
when 20N of Force pushes it.
Weight: Problem Set #F4
1. What is the weight of a 60kg person?
2. What is the weight of the 10kg object?
3. A 4kg and a 6kg object fall from a plane. How much
more Force will the 6kg object hit the ground with than
the 4kg object?
4. The 4kg and 6kg object both fall from a plane 10,000 m
above the ground. Which one will hit first?
5. Find the weight of a 300g object (in Newtons)?
6. An object weighs 10,000N on an unknown celestial
body, but only has a mass of 0.5 kg. What must be the
acceleration of gravity on this celestial body?
7. Find the acceleration due to gravity on the moon if
gravity on the moon is 1/6 of earths 9.8 m/s2?
8. Use your answer from the previous problem to find the
weight of a 90 kg object on the moon.
9. Find the mass of a plane whose weight is 4x105N?
10. If it takes 2s for a 10kg object to fall 100 m from rest on
an unknown planet, what is the planet’s acceleration of
gravity?
Student Learning Survey
1.
Before taking the test, how confident did you feel about your
understanding of Kinematics (motion)?
2. After taking the test, how confident did you feel?
3. Do you still try to succeed in this class? If not, what made you stop
trying?
4. I learned Physics the best when Mr. Ancalade did…….
5. Do you do homework? If you do, does it help? If you don’t, why don’t
you do homework?
6. If you did not turn in the cart and mass lab, why didn’t you? If you did
not complete any portion of the lab, what was the reason?
7. I spend _____ minutes on Physics homework per night.
8. I spend ______ minutes studying for tests.
9. I spend ______ minutes studying for quizzes.
10. Is it helpful when Mr. Ancalade does problems on the board? If yes,
explain how it helps. If no or not really, what are the reasons it doesn’t
help or only helps a little?
11. When I don’t understand how to do something in the class, what do I
do? If you don’t ask your peers or myself, what are your reasons?
N’s 3rd Law: Tug-of-War
To get a Full 10 pts. complete every section
with questions. That does not include the
explain section (which is lecture) or the
Evaluate Section (I will grade this section
separately) Write on a separate sheet.
•
Figures 6 (a) and (b): A student and a partner each pull on the opposing force-meters and observe that they show the same
reading. In the second scenario, one student holds his force-meter still, while the partner pulls his force meter to the right.
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Figures 7 (a) and (b): Students predict the reading on the force meter in each of the two scenarios depicted prior to testing.
Engage
What will happen to the motion of each chair when one of the students on the rolling chair pushes the other student on the
rolling chair. Will it matter which student pushes? Justify your answer. Tell me your reasoning.
Explore
Students attach their force-meters with rubber bands or string and record…
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the reading on each force-meter when both students pull (Figure 6 a.)
the reading on each force-meter when one student keeps his force-meter stationary while the other student pulls (Figure 6 b.)
Explain
Newton’s 3rd Law mini-lecture
Elaborate
Recreate the Figures 7(a) and (b). Write predictions for the force-meter readings for each of the two scenarios in Figure 7 .
Next, test your predictions, discuss your results in a group and be ready to participate in a discussion about these results.
Evaluate
Newton’s 3rd Law Assignment: #F5 Due Monday
Newton’s
rd
3
Law Notes
1. Using your Engage Experience, define Newton’s 3rd Law - 3
minutes.
2. Discussion - 2 minutes
Newton’s 3rd Law:
Definition: For every action (Force)
there is an equal and opposite
reaction (opposing Force)
Equation
FBA = -FAB
B
FBA
A
FAB
Where FBA is the Force of B on A
and FAB is the Force of A on B
Example
1.An object on a table is pushing down
on the table because of gravity and the
table is pushing up on it with normal
force.
2. The Force of gravity occurs when there
are 2 masses, each of them pulling on
each other with an equal and opposite
force.
3. Friction and a Car’s tires.
Non-Example
Trying to move from one point to
another in space by waving your
arms and legs furiously.
Notes 5 mins
#F5