AP PhysicsMonday 13.10.21Standards: 2c2 Students should understand the motion of projectiles in a uniform gravitational field.

Objective: SWBAT solve 2D Relative Motion Problems

Agenda1. Warm Up2. N’s 3 Laws3. Forces in Equilibrium4. Tension in a String

HomeworkRelative Motion 2-5 p.29

Warm UpIn a rescue attempt, a hovering helicopter drops a life preserver to a swimmer being swept downstream by a river current of constant velocity v. The helicopter is at a height of 9.8 m. The swimmer is 6.0 m upstream from a point directly under the helicopter when the life preserver is released. It lands 2.0 m in front of the swimmer. How fast in the current flowing? Neglect Air resistance. a) 13.7 m/s b) 9.8 m/s c) 6.3 m/s d) 2.8 m/s e) 2.4 m/s

AP PhysicsTuesday 13.10.22 Standards: 2c2 Students should understand the motion of projectiles in a uniform gravitational field. Objective: SWBAT solve problems involving relative velocity.

Agenda1. Warm Up2. Diagram an AP Free

Response Question

HomeworkStudy for Exam

Warm UpWhat are the 3 equations of motion? Write them down without looking at notes or asking your neighbors?

AP PhysicsWednesday 13.10.23Standards: 2c1 Students should understand the motion of projectiles in a uniform gravitational field.

Objective: SWBAT score 5’s on this test.

Agenda1. Warm Up2. Take Kinematics Test

HomeworkNA

Warm UpHow did you study for the Test Last night? 3 min.

AP PhysicsThursday 13.10.24Standards: B1 Static Equilibrium 1st Law, B2 students understand the relationship between force & acceleration. Objective: SWBAT find solutions to balancing forces problems.

Agenda1. Warm Up2. N’s 1st Law Reading 3. 1st law worksheet

HomeworkBalancing Tension Force Worksheet 3a

Warm UpWhat do you know about forces. Fill up the box. If you know little, ask some questions about forces.

AP PhysicsFriday 13.10.25Standards: 2b1 Draw a well labeled, free-body diagram. Objective: SWBAT create free body diagrams from written and drawn scenarios.

Agenda1. Warm Up2. Net Force & Free Body

Diagrams3. Practice In Class p.32, 1-3

HomeworkNewton’s 2nd Law Practice

Warm UpFind the missing Tension Forces for this system at equilibrium.

50 kg

45°

T2

T1

How to complete the lab write Up1. Come up with a question or hypothesis that you think you can prove. : ex. hyp. The

3 equations of motion will predict the motion of a following marble enabling us to break an egg.

2. Write down materials & procedures used and write down your procedure for setting up the experiment and implementing the experiment. (Do not include anything about calculations in this section)

3. Data: Use the scant information that you have to make a parabolic graph that represents the position of the marble. We do not have time data so we will just graph vertical and horizontal position y vs. x

4. Questions you will need to answer in your Calculations portion of the lab: - 1. What was the projectile’s initial velocity? - 2. How long was the projectile in the air before it hit the egg? - 3. Find the components of velocity of the marble as it goes through each of the three rings

and as it hits the egg - 4. What was the projectile’s final speed and angle as it hits the egg?

5. Analysis: In this section just justify your results using data. This entails evaluating your hypothesis as true, false, or inconclusive and provide it with actual data. One thing you might try proving is that the motion is parabolic. It may help depending on whether you are arguing for true, false, or inconclusive.

6. Conclusion: Summarize your results: Include important data that you got from the lab. Talk about and name some sources of error. Talk about and name any design changes or improvements you’d make to the lab.

New AP Lab Write Up FormatSection 4 3 2 1Question/Hypothesis The central question the lab is

asking is stated along with a plausible hypothesis

The central question is stated and something resembling a hypothesis is stated

Only the central question is stated

The section is missing or contains the wrong central question.

Materials/Procedures The procedures are written step by step in complete sentences and the materials are clearly listed.

The procedures and materials are listed but unorganized. The procedure does not explain the lab

Either the procedures or the materials are incomplete.

Only procedures are present, or only materials are present.

Data Collection The lab contains a table and a graph that represents the data accurately and is labeled correctly with the equation of the line written.

The lab contains a table and a graph but it may be missing some labels and the graph may not be done correctly.

The lab is missing a graph completely.

The data is incomplete.

Calculations Students have all calculations completed, with work shown, and they are correct.

Students have all calculations completed and at least half are done correctly and all work is shown.

Students do not have all calculations completed, and little work is shown.

Calculations section is mostly or entirely missing.

Analysis The student gives evidence from their lab data why their hypothesis is true, false, or inconclusive. The discuss the relationships between the variables that were graphed and if linear they write down the equation of the line.

The students gives evidence from their lab data and attempts to prove that the hypothesis is false, true or inconclusive, but the data is misapplied and doesn’t support their claim. For linear graphs, no equation is given.

This section discusses whether the hypothesis is true, inconclusive, or false but no data is used to support the hypothesis and any reference to the graph or the data is too general to be helpful.

This section is omitted or the student may mention the hypothesis and its validity, but doesn’t explain or the explanation is not plausible

Conclusion The conclusion includes a summary of your lab results, (which will include numbers or equations), gives %error and discusses sources of error. It also gives a suggestion about how to improve the lab.

The conclusion includes a summary of your lab results. It includes data. % error is given. Either and least 1 source of error discussed or a suggestion is given to improve the lab.

The conclusion includes a summary and either % error, or mentions types of error, or mentions improving the experiment.

The conclusion is omitted or only includes a brief summary.

Group Poster/Formal Problem Write Up Rubric

Section 4 3 2 1

Equations All Equations required for the problem are written down

Not all equations used are written down

---- No equations are written down

Givens All givens are written down correctly. The unknown is also written down correctly

The givens are written down but the unknown is omitted, or all givens and unknowns are written down but there are slight errors like incorrect sign or no units.

Some givens and/or the unknown are omitted Units may also be missing

Either this section doesn’t exist or the givens are written without their symbols.

Diagram The diagram represents the problem and uses all of the conventions learned in class correctly. All of the givens are represented in the diagram.

The diagram represents the problem, but some of the conventions for representing the givens are violated.

One or more given is not represented at all in the diagram, some conventions are misrepresented, and the diagram may not represent the problem correctly.

This section is missing or if present most conventions for diagrams have been violated, and the diagram does not represent the problem in a meaningful way.

Solution All work is shown from plugging the numbers into the equations to cancelling out units and of course obtaining the correct answer with correct units.

Any minor mistakes such as incorrectly cancelling out units or omitting units from a part of the problem are the only errors. The answers are correct with the correct units. The answer may omit a negative sign and receive this score.

The answer is partially correct or incorrect, the work is fragmented and units are not carried through the problem. Also, the answer can be completely correct and very little work is shown.

No work is shown. The can be correct or incorrect, it doesn’t matter. Also, work is shown but the wrong equations are used and the work does not come close to representing the problem, or answering the question.

Creativity/Neatness The poster just looks good. The drawings may not be workings of art but significant effort has been put into presentation. No cross outs or large blemishes. The poster is organized neatly.

The poster has one major blemish but that is all. The poster has some organization, and it may not be very aesthetically pleasing but it is clear and readable.

The poster is pretty messy with multiple crossouts and other large blemishes. It is somewhat readable.

The poster is messy, unorganized, no visible effort has been taken to make the work readable.

Newton’s First LawThe Law of Inertia – “In the absence of an unbalanced applied force (Fnet=0), a body at rest remains at rest, and a body already in motion remains in motion with a constant velocity (constant speed and direction)

If there is no net force an object initially at rest will stay at rest.If there is no net force and object initially moving will stay moving.

This means that objects resist changes in their motion. It is hard to make objects speed up or slow down. You have to force them to do it, by applying a force.

AP Kinematics Test Review: Poster or Formal Problem Write Up

A cannonball is shot with an initial speed of 35 m/s at a launch angle of 35° toward a castle wall 110 m away. The height of the wall is 40m. Assume that effects due to the air are negligible. (for this problem use g=9.8m/s2).a) Show that the cannonball will strike the castle wall. (This

means using no numbers. You can do this last if you like)b) How long will it take for either the cannonball to strike the

wall? t=3.82sc) At what height above the base of the wall will the

cannonball strike? hw(cb)=5.2m

Conventions for Physics Diagrams

for drawing

distance

horizontal displacement

vertical displacement.

d

Δx

Δy

for drawing

speed

velocity

for drawing

mass

acceleration

time

5kg

a

Δx

t

vs

v

Types of ForcesForce 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 or N 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 or T 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 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 or W 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

Electric FE Force between atoms with electric charge (protons & electrons)

Like charges repel +Opposite charges attract -

Magnetic FB Force between magnetic poles & force created when electric current is in flux.

Same Pole repelsOpposite Pole Attracts

among others

Newton’s 2nd Law of Motion

When you are dealing with Force Problems you need to add up all of the x components of Force and all of the y components of Force separately.

we write it like this:Fx= Fx1+Fx2+Fx3+Fx4+…FxN =Fnet x all these fancy symbols mean you add up all of the forces in the x direction to get the total force acting on the object. Fy= Fy1+Fy2+Fy3+Fy4+…FyN=Fnet y same for the y direction.

Get used to breaking Force vectors into components to solve problems. You can’t deal with vectors at an angle without breaking them into components.

Free Body Diagrams

How to draw a free body diagram.

1. Represent the object of interest with a dot.

2. Make an arrow for every Force acting on that object in the direction that the Force is pointing.

2. Only include Forces in this type of diagram. This is separate from previous diagrams we have used to solve problems.

3. The Arrows should never point towards the object.

3. Label the Forces.

W

Fap

30°

Free Body Diagram Practice ProblemIn the early morning, a park ranger in a canoe is observing wildlife on the nearby shore. The Earth’s gravitational force on the ranger is 760N downward and its gravitational force on the boat is 190N downward. The water keeps the canoe afloat by exerting a 950N force upward on it. Draw a free body diagram of the canoe.

Extra Practice: p.42 Cracking the AP Physics B Exam

Free Body Diagram Practice3bFor each of the following problems create a free body diagram. Where asked, answer questions.1. A piano falls from the sky and air makes it reach terminal velocity2. A cart from an amusement park ride is accelerated up at an angle θ. Assume

friction is negligible, but air resistance is significant.

3. The cart from problem 2 drops at a very steep angle of ϕ.4. A 70kg rock falls from the cliff and the air provides an upwards force of 30N.

5. A 65kg skydiver opens her parachute. Air resistance to her body is 20 N and the Lift Force is 617N. What is the Net Force acting on her?

6. A 25kg child rolls down a hill angled 60° to the horizontal. Friction is significant.

7. A 15kg chandelier is attached to the ceiling using a cable.

8. A 25kg child is hanging stationary from monkey bars. One arm is angled at 30° and the other arm is angled at 60°.

9. **A cart is sitting on a table and attached to a pulley by a string. The other side of the pulley has a mass M attached to the bottom. Both objects are stationary. Find the free body diagram of the cart and of the mass separately.

Newton’s 2nd Law Practice 3c1. A car is accelerated east with a 2000 N Force. Friction resists the car’s motion with 120N and air resistance

contributes another 35 N. What is the net Force acting on the car?2. A bike rider pushes his/her bike pedals with a Force of 200N. This only accelerates the bike at 1m/s2. If s/he

and the bike have a combined mass of 150kg, how much resistive Force was acting on the bike? 3. How much is A different car with a mass of 750 kg accelerates at a rate of 2m/s2. If Friction resists the

motion with 180 N of force and air resistance with another 35 N, how much Force was applied by the engine?

4. A toy 0.5 kg toy car is accelerated from rest with a 20 N force for 3 seconds. How far did the car travel? 5. A child is on a table flicking marbles to see how far they will fly. A 0.25 kg marble is flicked from rest by the

child. The child applies 4 N of Force with her finger that lasts 0.5 seconds. Afterwards, if the marble travels at a constant velocity until it flies off of the 2 m high table (assume no friction), how far away from the table did the marble land?

6. A rope of negligible mass supports a block that weighs 30 N, as shown above. The breaking strength of the rope is 50 N. The largest acceleration that can be given to the block by pulling up on it with the rope without breaking the rope is most nearly what?

7. A horizontal, uniform board of weight 125 N and length 4 m is supported by vertical chains at each end. A person weighing 500 N is sitting on the board. The tension in the right chain is 250 N. What is the tension in the left chain?

8. The cart of mass 10 kg shown above moves without frictional loss on a level table. A 10 N force pulls on the cart horizontally to the right. At the same time, a 30 N force at an angle of 60° above the horizontal pulls on the cart to the left. What is the magnitude of the horizontal acceleration of the cart?

9. A 100 N weight is suspended by 2 chords as shown above. The Tension on the slanted chord is?10. When an object of weight W is suspended from the center of a massless string as shown above, the tension at any point

in the string is?

#10 #9

#8

#7