Monday,
October 28, 2013
Physics
Standards: 1c Students know how to
apply F=ma to solve one-dimensional
motion problems that involve
constant forces.
Learning Objective: SWBAT design
an experiment to test Newton’s 2nd
Law
Agenda:
1. Warm Up
2. Review HW
3. Newton’s 2nd Law Lab
Warm Up
What is the net force on the
box?
1N
3N
8N
4N
Homework
Begin working on HW Problems
Worksheet #F2: Due Wednesday
Tuesday,
October 29, 2013
Physics
Standards: 1c Students know how to
apply F=ma to solve one-dimensional
motion problems that involve
constant forces.
Warm Up
If the cart from yesterday’s
lab is pushed down by 3 N
of force and it has a mass of
.15 kg, how fast would it
accelerate?
Learning Objective: SWBAT design
an experiment to test Newton’s 2nd
Law
Agenda:
1. Warm Up
2. Review Lab Day 1
3. Newton’s 2nd Law Lab Continued
Homework
Begin working on HW
Problems Worksheet #F2:
Due Wednesday
Wednesday,
October 30, 2013
Physics
Standards: Standards: 1c
Students know how to apply
F=ma to solve onedimensional motion
problems that involve
constant forces.
Learning Objective: SWBAT
take 2 sets of data to show
how acceleration is affected
by changing mass.
Agenda:
1. Warm Up
2. Turn in Part 1 of lab
3. Write a hypothesis for
question 2 and 3
4. Collect Data For Part 2 & 3
Warm Up
If you want to prove that an
object is accelerating, what
data will you collect? What
shape will your graph be?
Homework
Problems Worksheet #F2: Due
Friday
Thursday,
October 31, 2013
Physics
Warm Up
What is the weight in N, of a
25g object? Remember to
change g-> kg 1000g=1kg
Standards: Standards: Standards: 1c
Students know how to apply F=ma to solve
one-dimensional motion problems that
involve constant forces.
Learning Objective: SWBAT create an
experiment testing the effect of mass on
acceleration.
Agenda
1. Review Part 2 Lab
2. Part 3 Cart & Masses Lab
Homework
Cart & Masses Lab Part 3
Friday,
November 1, 2013
Physics
Standards: 1c Students know how to
apply F=ma to solve one-dimensional
motion problems that involve constant
forces.
Warm Up
If an object’s mass is 20 kg,
and it is being pushed with a
Force of 100N, what will be
the object’s acceleration?
Learning Objective: SWBAT
reflect and discuss lab results
and apply what they’ve
learned to answer questions.
Agenda:
1. Warm Up
2. Lab Report Review
3. Turn in Part 2 & 3 of Lab
Agenda:
1. Warm Up
Homework
#F2 & #F3
Symbols, units and
equations Study Guide
Equations:
Constant Velocity
v=
Dx
Dt
d
v
=
Dy = y f - yi s t
Dx = x f - xi
--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
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
Forces
Fnet = ma
Fg = W = mg
Fnet = F1 + F2 + F3 +...Fn
Profile of A Force
• Force is a vector (direction matters!)
• The Units of Force are Newtons (N) or it can also
be written as kilograms times meters per second
squared (kg*m/s2)
• Equation: Fnet=MA
o Fnet is the result of adding all
o of the forces together.
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
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
N
Balancing Forces
W
E
S
• We know that if Forces are balanced or
non-existent, an object will travel at
constant speed or at rest.
• If they are imbalanced, they will go in the
direction of the Net Force or Total Force in
one direction.
• Net Force means: add up all of the Forces.
• Force is a vector (direction matters, so) add
the following forces.
4N
5N
7N
#F1a
Calculating Net Force
Force each of the following draw a diagram for each and solve.
1.
2.
3.
4.
5.
5 N West, 3 N West Fnet=?
15 N West, 10 N East, 7 N West Fnet=?
2 N West, 1 N East, 7 N West, 8 N East Fnet=?
4 N North, 4 N South, Fnet=?
6 N North, 2 N West, 4N East, 7 N South Fnet=?
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?
Carts & Masses
Engage - You will construct gliders to be launched from a catapult at the
end of the unit but not yet–at this point in time, Today, you are going to
design an experiment to determine what happens to an object when
there’s a net force acting on it.
Explore - Students are shown the experimental setup (Figure 4).
Respond following questions, and provide an explanation for your thoughts:
o What will happen to the cart when there is a force applied to it?
o What if the applied force is increased? What about the cart’s
motion will change?
o What if the cart’s own mass is increased? How will its motion
change?
Test - Design and execute experiments to test your hypothesis from the
explore section (at least 5 trials for each hypothesis).
Explain – Make a graph for each set of data. You decide what you think
you should graph.
Elaborate
Class Discussion Questions
Why is it a good idea to do multiple trials?
o “What aspects” changed from one trial to the next?
o What variable did you change on purpose?
o What variable changed as an effect of changing your
independent variable?
Newton’s 2nd Law Questions:
o What happens if we apply a net force on an object?
o What happens if that net force is increased?
o What happens if the mass of the object itself increases?
We have a mathematical expression for this: Fnet = ma.
Evaluate
Complete HW #F2
Figure 4.
Experimental
setup for cart &
mass activity
#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.)
Cart and Masses Lab Instructions
EVERY PERSON WILL TURN IN THE FOLLOWING
• Part 1 Due Today
o Use Δx=(1/2)at2 to find the average acceleration
o Use your x vs t graph to prove the object is accelerating
• Part 2 Due Thursday
• All data must be collected IN CLASS
• Use Fnet=ma to find the acceleration. Compare this to the average
acceleration you can calculate from Δx=(1/2)at2. Explain the differences
• Graph Fnet vs m and use this graph to prove your hypothesis
• Part 3 Due Thursday
• All data must be collected IN CLASS
• Use Fnet=ma to find the acceleration. Compare this to the average
acceleration you can calculate from Δx=(1/2)at2. Explain the differences.
• Graph Fnet vs m and use this graph to prove your hypothesis.
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.