AP PHYSICSMONDAY 14.11.03STANDARDS: KINEMATICS 1D & 2D: BIG IDEA 3

Agenda:

1. Warm Up

2. Review HW #5

3. Understanding Friction Lab

HomeworkTurn in HW Monday

Warm UpA 3100 N Force is applied by the engine of a 1000 kg car to push it up a 12 degree incline. If the net acceleration of the car upwards at 0.5 m/s, what is the Force of friction on the car and what is the coefficient of friction between the car and the road?

Standards: 3a3 A force exerted on an object is always due to the interaction of that object with another object

I –Independent Resilient IndividualsRST.11-12.9 Synthesize information from a range of sources into coherent understanding of a process, phenomenon, or concept,…

Learning Goal: SWBAT calculate the coefficient of friction between a mass and a table.

AP PHYSICSTUESDAY 14.11.06I- INDEPENDENT, RESILIENT IND.STANDARDS: 3A3 A FORCE EXERTED ON AN OBJECT IS ALWAYS DUE TO THE INTERACTION OF THAT OBJECT WITH ANOTHER OBJECT

RST.11-12.9 SYNTHESIZE INFORMATION FROM A RANGE OF SOURCES INTO COHERENT UNDERSTANDING OF A PROCESS, PHENOMENON, OR CONCEPT,…WHST.11-12.7: RESEARCH TO AID IN PROBLEM SOLVING

Agenda:

1. Warm Up

2. Review HW

3. KAP #7

4. Friction Inquiry

HomeworkFAP#7

Warm Up

Learning Goal: SWBAT create net force expressions from free body diagrams

The ball below is 6kg and rolls down the frictionless ramp. Air resistance is negilgable. What is the acceleration of the ball?

60°

AP PHYSICSWEDNESDAY 14.11.05

STANDARDS: 3A3 A FORCE EXERTED ON AN OBJECT IS ALWAYS DUE TO THE INTERACTION OF THAT OBJECT WITH ANOTHER OBJECT

I –INDEPENDENT RESILIENT INDIVIDUALS

RST.11-12.9 SYNTHESIZE INFORMATION FROM A RANGE OF SOURCES INTO COHERENT UNDERSTANDING OF A PROCESS, PHENOMENON, OR CONCEPT,…

Agenda:

1. Warm Up

2. Review HW

1.Learning Goal: SWBAT find the coefficient of friction between the ramp and the cylinder Homework

FAP #5 & FAP#6

Warm Up

The ball below is 6kg, the coefficient of friction is 0.6 and air resistance is negligible. What is the acceleration of the ball down the ramp.

60°

AP PHYSICSTHURSDAY 14.11.06I- INDEPENDENT, RESILIENT IND.STANDARDS: 3A3 A FORCE EXERTED ON AN OBJECT IS ALWAYS DUE TO THE INTERACTION OF THAT OBJECT WITH ANOTHER OBJECT

RST.11-12.9 SYNTHESIZE INFORMATION FROM A RANGE OF SOURCES INTO COHERENT UNDERSTANDING OF A PROCESS, PHENOMENON, OR CONCEPT,…WHST.11-12.7: RESEARCH TO AID IN PROBLEM SOLVING

Agenda:

1. Warm Up

2. Review HW

3. Continue Friction Lab

HomeworkFriction Quiz Tomorrow

Warm Up

Learning Goal: SWBAT calculate the angle of slippage of an object on a ramp from your previously measured friction coefficient.

Find the angle of a stationary object on a ramp if the mass is 3 kg and the coefficient of static friction is 0.7.

Agenda

1. Warm Up

2. Friction Quiz

3. Simple Pulley

HomeworkFAP #8

Warm UpA skateboarder drags a 5 kg box at a constant speed and at an angle of 20 degrees to the horizontal. If the coefficient of kinetic friction is 0.27, how much Force will the skateboarder need to apply to maintain his/her speed.?

Learning Goal: SWBAT draw a free body diagram of a simple pulley/box system.

AP PhysicsFriday 14.11.07Standards: 3a3 A force exerted on an object is always due to the interaction of that object with another objectRST.11-12.4 Meaning of symbols, key terms, technical jargonProblem Solvers

θ

TYPES OF FORCESForce Symbol Definition Direction

Friction f or Ff Resistive Force. Comes from rubbing against or sliding across surfaces.

Parallel to the surface and opposite the direction of sliding

Normal N or 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 T or 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 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 W or 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

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

Applied Force FAP A Force applied by a person, thing, or individual that does not fall into any of the above categories

any

FAP #6 NET FORCE PROBLEMS

1. A rope of negligible mass supports a block that weighs 30 N, as shown to the right. 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?

2. The cart of mass 10 kg shown below 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?

3. A 100 N weight is suspended by 2 chords as shown above. The Tension on the slanted chord is?

4. When an object of weight W is suspended from the center of a massless string the tension at any point in the string is? #4

#3

#2

#1

FAP#4 FRICTION ON AN INCLINED PLANEA block of mass 5 kilograms lies on an inclined plane, as shown above.

The horizontal and vertical supports for the plane have lengths of 4 meters and 3 meters, respectively. The coefficient of friction between the plane and the block is 0.3. The magnitude of the force F necessary to pull the block up the plane with constant speed is most nearly.

FAP #5An empty sled of mass 25 kg slides down a muddy hill with a constant speed of 2.4 m/s. The slope of

the hill is inclined at an angle of 15° with the horizontal as shown in the figure above.

a. Calculate the time it takes the sled to go 21 m down the slope.

b. On the dot below that represents the sled, draw/label a free-body diagram for the sled as it slides down the slope

Calculate the coefficient of friction between the sled and the muddy surface of the slope.

e. The sled reaches the bottom of the slope and continues on the horizontal ground. Assume the same coefficient of friction.

i. In terms of velocity and acceleration, describe the motion of the sled as it travels on the horizontal ground.

ii. On the axes below, sketch a graph of speed v versus time t for the sled. Include both the sled's travel down

the slope and across the horizontal ground. Clearly indicate with the symbol t the time at which the sled leaves

the slope.

UNDERSTANDING HOW THE FORCE OF FRICTION WORKS #16a. Find the coefficient of friction down a ramp (using symbols

only) μs=?

b. Find the coefficient of kinetic & static friction between a horizontal ramp and a cylinder. (Do this by dragging the cylinder from rest with a Forcemeter & dragging the cylinder while moving with a Forcemeter. Demo will be shown in class.) mass (kg)

fs μs fk μk

c. Next we want to prove that our equation for letter a is actually physically true. i. We found μs experimentally in part b, so plug your values for

μsn into your equation from part a. Solve for θ’s. ii. Now we can find the angle where your masses should

begin to slide.iii. Now we can measure the angle that the masses will

actually begin to slide. iv. Calculate % difference between the measured and calculated angles.

16 CONTINUED

c. Next we want to prove that our equation for letter a is actually physically true. i. We found μs experimentally in part b, so plug your values for

μsn into your equation from part a. Solve for θ’s.

ii. Now we can find the angle where your masses should begin to slide.

iii. Now we can measure the angle that the masses will actually begin to slide.

iv. Calculate % difference between the measured and calculated angles.

mass (kg)

Ramp Angle

tan θ μs exp. % error

% uncertainty = measured – actual actual

HW: FAP#7

After you create each free body diagram, use your free body diagram to make an Fnet=ma expression in the x direction and in the y direction.

Ex

``` `

FN

Fg

FAPFFFAR

Fnetx=Fap-Ff-FAR=macar-x-direction

Fnety=FN-Fg=macar y-direction