DAY 51
NGSS Standard (this is what we're learning with this unit)
Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. [Clarification Statement: Examples of data could include tables or graphs of position or velocity as a function of time for objects subject to a net unbalanced force, such as a falling object, an object sliding down a ramp, or a moving object being pulled by a constant force.] [Assessment Boundary: Assessment is limited to one-dimensional motion and to macroscopic objects moving at non-relativistic speeds.]
#Goals: SWBAT...
1. Draw correct FBD's, with appropriate vector magnitude and direction.
2. Use FBD's to find Net Force
3. Describe the relationship between mass, net force, and acceleration
Warm-Up (3min)
When a person shoots a rifle, the forces on the bullet and the rifle are equal and opposite. Why does the bullet accelerate much faster than the rifle? Which law(s) does this example illustrate?
CLASSWORK
1. 051A: Quiz 9: Newton's Laws Problem Solving.
2. 051B: Knowledge Inventory: Newton’s Laws & Forces
Instructions: Your job: Read the instructions on the handout, then complete the Pre-Inventory section of the chart.
Handout is on Schoology
3. If you finish early, work on the Learning at Home (HW) video (see below)
Learning at Home (HW)
051C: Review the concept of the Newton. Take notes and answer the following three questions
1. Did I take notes?
2. What common household object does the instructor use to show the force of one Newton?
3. Solve the force problem before the instructor does. Check his answer to make sure it's correct
https://www.youtube.com/watch?v=A2kXTX3rnKk
#052B: Concept Builder: Fnet = m•a
Objective: Students will use Newton’s 2nd Law equation (Fnet = m•a)to
Complete “Activity #1: Basic Problems” and “Activity #2: Different Masses”
Write your labeled diagrams (AKA answers) in your notes. You should have a total of six correct diagrams.
Link to activity: LINK
#Goals: SWBAT...
1. Use FBD's to find Net Force
2. Solve for forces using mass, net force, and acceleration
3. Define Newton's 3rd law
Warm-Up (4min)
Read the scenario below, then answer the questions at the end
"Lee Mealone is sledding with his friends when he becomes disgruntled
by one of his friend's comments. He exerts a rightward force of 9.13 N
on his 4.68-kg sled to accelerate it across the snow. If the acceleration
of the sled is 0.815 m/s/s, then what is the coefficient of friction between
the sled and the snow?"
List the forces present in this example
Draw the FBD
Which equations would you use in your process to find the coefficient
of friction (µ)
CLASSWORK
1. #051A: Practice with Solving FBD's
A. find the coefficient of friction for the warm-up problem
B. In a Physics lab, Ernesto and Amanda apply a 34.5 N rightward force to a
4.52-kg cart to accelerate it across a horizontal surface at a rate of 1.28 m/s/s.
Determine the friction force acting upon the cart.
2. #051B: Newton's 3rd
For every force applied by an object, there's an equal and opposite force
on that object.
Notes: link
Edpuzzle: EDpuzzle
3. #051C: Identifying Interaction Pairs
1. While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?
2. For years, space travel was believed to be impossible because there was nothing that rockets could push off of in space in order to provide the propulsion necessary to accelerate. This inability of a rocket to provide propulsion is because ...
a. ... space is void of air so the rockets have nothing to push off of.
b. ... gravity is absent in space.
c. ... space is void of air and so there is no air resistance in space.
d. ... nonsense! Rockets do accelerate in space and have been able to do so for a long time.
3. Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases that expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ...
a. greater than the acceleration of the bullet.
b. smaller than the acceleration of the bullet.
c. the same size as the acceleration of the bullet.
4. In the top picture (below), Kent Budgett is pulling upon a rope that is attached to a wall. In the bottom picture, Kent is pulling upon a rope that is attached to an elephant. In each case, the force scale reads 500 Newton. Kent is pulling ...
a. with more force when the rope is attached to the wall.
b. with more force when the rope is attached to the elephant.
c. the same force in each case.
Examples of Interaction Force Pairs
Read the following, and list all the interaction pairs you find:
A variety of interaction force pairs are evident in nature. Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. But a push on the water will only serve to accelerate the water. Since forces result from mutual interactions, the water must also be pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards). Interaction force pairs make it possible for fish to swim.
Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. Since forces result from mutual interactions, the air must also be pushing the bird upwards. The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for birds to fly.
Consider the motion of a car on the way to school. A car is equipped with wheels that spin. As the wheels spin, they grip the road and push the road backwards. Since forces result from mutual interactions, the road must also be pushing the wheels forward. The size of the force on the road equals the size of the force on the wheels (or car); the direction of the force on the road (backwards) is opposite the direction of the force on the wheels (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for cars to move along a roadway surface.
At Home Learning (HW)
Complete all of the above...
#051D: Edpuzzle Video: https://edpuzzle.com/media/5808f3259935d0833a0236e3
NGSS Standard (this is what we're learning with this unit)
Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship amongthe net force on a macroscopic object, its mass, and its acceleration. [Clarification Statement: Examples of data could include tables or graphs of position or velocity as a function of time for objects subject to a net unbalanced force, such as a falling object, an object sliding down a ramp, or a moving object being pulled by a constant force.] [Assessment Boundary: Assessment is limited to one-dimensional motion and to macroscopic objects moving at non-relativistic speeds.]
Goals: SWBAT...
1. Momentum - Is It Conserved?
Warm-Up (5min):
A clown is on the ice rink with a large medicine ball. If the clown throws the ball forward, then he is set into backwards motion with the same momentum as the ball's forward momentum. What would happen to the clown if he goes through the motion of throwing the ball without actually letting go of it? Explain.
Dale, Mel, and Shanelle are astronauts on a spaceship. They each have the same mass and the same strength. Dale and Mel decide to play catch with Shanelle, intending to throw her back and forth between them. Dale throws Shanelle to Mel and the game begins. Describe the motion of Dale, Mel and Shanelle as the game continues. If we assume that each throw involves the same amount of push, then how many throws will the game last?
CLASSWORK
1. #051A: Is momentum conserved? Conclusion
complete collecting data for #050B
Stuck? Here are two videos to help you through the process.
Complete the conclusion. Also, answer the following questions at the end of your conclusion:
1. Did your initial and final momenta match exactly? If they didn't, you made an error (which is okay).
2. What do you think caused your error?
3. What effect did your error have on your data?
2. #051B: Momentum Conservation Practice Problems
solutions for the practice problems are here: LINK
1. When fighting fires, a firefighter must use great caution to hold a hose that emits large amounts of water at high speeds. Why would such a task be difficult?
A large truck and a Volkswagen have a head-on collision.
a. Which vehicle experiences the greatest force of impact?
b. Which vehicle experiences the greatest impulse?
c. Which vehicle experiences the greatest momentum change?
d. Which vehicle experiences the greatest acceleration?
If a ball is projected upward from the ground with ten units of momentum, what is the momentum of recoil of the Earth? ____________ Do we feel this? Explain.
If a 5-kg bowling ball is projected upward with a velocity of 2.0 m/s, then what is the recoil velocity of the Earth (mass = 6.0 x 1024 kg).
A 120 kg lineman moving west at 2 m/s tackles an 80 kg football fullback moving east at 8 m/s. After the collision, both players move east at 2 m/s. Draw a vector diagram in which the before- and after-collision momenta of each player is represented by a momentum vector. Label the magnitude of each momentum vector.
In an effort to exact the most severe capital punishment upon a rather unpopular prisoner, the execution team at the Dark Ages Penitentiary search for a bullet that is ten times as massive as the rifle itself. What type of individual would want to fire a rifle that holds a bullet that is ten times more massive than the rifle? Explain.
A baseball player holds a bat loosely and bunts a ball. Express your understanding of momentum conservation by filling in the tables below.
At Home Learning (HW)
1. You should have finished the Lab in class today. I'll be collecting it Thursday
2. Take notes/answer edpuzzle questions on the following:
a. (6:46) Introduction to Elastic and Inelastic Collisions - EDpuzzle
b. (5:39) Introductory Conservation of Momentum Explosion Problem Demonstration - EDpuzzle
3. QUIZ tomorrow :) Momentum and Impulse. Review by completing the questions in 051B (solutions for the practice problems are here: LINK), and by reviewing the problems we solved in 049A and 049B