Dynamics and Statics What is the resultant velocity

Dynamics and Statics {

What is the resultant velocity vector on a boat that is traveling at 10 m/s north and is being blow by the wind 0. 5 m/s east? Include the magnitude and angle. Bellringer

Learn more vocabulary that will help you solve dynamics and statics problems Practice identifying objects in a system Concurrent forces problems Objectives

Kinematics Test In order to get any points back you must complete the following by next Friday (10/17) 1. Add the correct equation and units when substituting where you forgot to on the Part Two to receive full points back. 2. Correct all problems you got wrong (Part One and Part Two) to receive half points back. 3. Hand them in to me in person during one of my free mods.

You get to pick the two other teams forces. Pick some numbers between 0. 1 N and 1. 962 N Also pick the angle between them. Pick some angle between 95 and 135 degrees The plastic hangers have a mass of 5 grams Lab #5

Bellringer – 2 mins to hand in Find the horizontal component of a 15 N vector that is 15 degrees above the horizon. DO STOP WORK

Learn more vocabulary that will help you solve dynamics and statics problems Practice identifying objects in a system Concurrent forces problems Objectives

Kinematics Test In order to get any points back you must complete the following by next Friday (10/17) 1. Add the correct equation and units when substituting where you forgot to on the Part Two to receive full points back. 2. Correct all problems you got wrong (Part One and Part Two) to receive half points back. 3. Hand them in to me in person during one of my free mods.

Robots?

Dynamics: The study of forces and motion Statics: The study of forces in static equilibrium Some words

Static: Not moving. Equilibrium: The condition of a system in which all competing influences are balanced (Net Force = 0) More words

System: A set of interacting or interdependent pieces forming one thing. Net Force: The overall force acting on a system (all the forces added together) Even more words

1. 2. 3. 4. If an object is moving at constant velocity is it in static equilibrium? What is the net force on an object that is moving at constant velocity? If an object is moving at constant velocity is it at equilibrium? If there is a non-zero net force on a system can it be moving at constant velocity? Checkpoint

Baseball in the catcher’s mitt. Your dinner on a table. Define all objects in each system.

Baseball in the catcher’s mitt. Your dinner on a table. Free-Body Diagrams

1. 2. 3. 4. For each of the following situations, specify the system and draw a free-body diagram. Label all forces, and indicate the direction of the acceleration and the net force. A skydiver falls downward through the air at constant velocity. (The air exerts an upward force on the person. ) You hold a softball in your hand move it up. Two people pushing equally on a table in opposite directions. Two equally strong huskies pulling a sled in the same direction. Practice

Demo Force and mass

Two identical huskies are pulling a sled through the snow. They are each pulling with a force of 40 N in the same direction. Neglecting friction (snow) what is the total net force on the sled? Happy Huskies

Two identical huskies are pulling a sled through the snow. They are each pulling with a force of 40 N in the opposite direction. Neglecting friction (snow) what is the total net force on the sled? Hateful Huskies

Two identical huskies are pulling a sled through the snow. They are each pulling with a force of 40 N at an angle of 90 degrees from one another. Neglecting friction (snow) what is the total net force on the sled? Hungry Huskies

What have our little husky buddies taught us? What is the maximum resultant of two forces and the angle between them? What is the minimum resultant of two forces and the angle between them? Humble Huskies

Concurrent Forces are the Regent’s exams fancy way of saying forces that act on a system at the same time. Concurrent Forces

Which pair of concurrent forces may have a resultant of 40 N? 1 N and 5 N 20 N and 10 N 20 N and 30 N 50 N and 5 N Which pair of concurrent forces may have a resultant of 20 N? 5 N and 10 N 20 N and 50 N 30 N and 5 N Concurrent Forces Examples

Two concurrent force of 50 N and X Newtons have a resultant of 100 N. Force X could be 10 N 40 N 90 N 160 N Two concurrent force of 40 N and X Newtons have a resultant of 100 N. Force X could be 20 N 40 N 80 N 150 N Concurrent Forces Examples

The resultant of two concurrent forces is minimum when the angle between them is 0 degrees 45 degrees 90 degrees 180 degrees As the angle between two concurrent forces is increased from 10 to 75 degrees, the magnitude of the resultant force decreases increases Remains the same Concurrent Forces Examples

Mary is holding a pillow with a mass of 0. 3 kg when Sarah decides that she wants it and tries to pull it away from Mary. If Sarah pulls horizontally on the pillow with a force of 10 N and Mary pulls with a horizontal force of 11 N, what is the horizontal acceleration of the pillow? Pillow Fight!

First identify the system and what is acting on it: Pillow Fight

Then draw a free body diagram: Pillow Fight

Then solve for the unknown: Pillow Fight

Finally; as always, evaluate the answer: Pillow Fight

Buddy is learning how to ice skate. He wants his momma to pull him along so that he has an acceleration of 0. 8 m/s^2. If Buddy’s mass is 27. 2 kg, with what force does his momma need to pull him? (Neglect any resistance between the ice and Buddy’s skates. ) Use the same steps as the pillow fight problem. Ice Skating

Bellringer – 2 mins to hand in What is the acceleration of a baseball (0. 145 kg) that is hit with a force of 150 N DO STOP WORK

Know the difference between weight and mass, and be able to solve problems. Objectives

Vector Quiz

Kinematics Test In order to get any points back you must complete the following by next Friday (10/17) 1. Add the correct equation and units when substituting where you forgot to on the Part Two to receive full points back. 2. Correct all problems you got wrong (Part One and Part Two) to receive half points back. 3. Hand them in to me in person during one of my free mods.

Use inertia and Newton’s first law of motion to explain this picture. (Write your response)

Car crash demo Newton’s First Law

An object’s weight is the gravitational force experienced by that object. Weight = Mass x Gravitational Field on Earth is 9. 81 m/s^2 So this is the same equation as F=ma What is weight?

How do scales find your weight? ? ? ? ? Scales are not accelerating so the net force on them must be zero. The scale pushes up with the same force that gravity pushes you down. This action reaction pair causes calibrated springs to stretch and turn a dial that displays your weight. Scales

Karan holds a golden puppy in each hand. Puppy A has a mass of 4 kg and puppy B has a mass of 12 kg. What upward forces do her two hands exert to keep the puppies at rest? If she then drops the two puppies, with what acceleration do they fall? (Ignoring air resistance. ) Comparing weights

Does an object’s mass change depending on what gravitational field it is in? Does an objects weight change depending on what gravitational field it is in? Changing mass

If you have a mass of 72 kg what is your weight, in Newtons, of Earth? What is the weight, in Newtons, on the moon? (The acceleration due to gravity there is 1. 62 m/s^2) So what’s the easiest way to lose some weight? ? What is the weight in Newtons on Jupiter? (The acceleration due to gravity there is 24. 79 m/s^s) Changing Weight Checkpoint

Gravity map of the Moon

What is the gravitational acceleration on a planet where a 4 kg mass has a weight of 16 N on the planet’s surface? What is the gravitational acceleration on a planet where a 2 kg mass has a weight of 8 N on the planet’s surface? Weight Training

If your weight on Earth is 500 N, what is your weight on a planet where the acceleration due to gravity is 6 m/s^2 Weight Training

It is impossible to be massless, but is it impossible to be weightless? ? No you always have a weight too. Sometimes it just doesn’t seem like you do. This is called apparent weightlessness. Weightlessness

Apparent Weightlessness means that there are no contact forces acting to support the object, and the object’s apparent weight is zero. What are contact forces? Any forces that need to be in contact with an object to exert a force on it. The feeling of weightlessness is most common when you or an object is in free-fall. Apparent Weightlessness

Big drops on rollercoasters Dips in airplanes Orbiting the Earth Going down a big hill Falling Examples

Review sheet Homework

Bellringer – 2 mins to hand in 1. 2. 3. What have you done to make sure your grade is what you want it to be? What will you do to improve your grade (or keep it at a 100)? What do you want your grade to be at the end of the quarter? (Can’t lower it) DO STOP WORK

Homework

Kinematics Test In order to get any points back you must complete the following by next Friday (10/17) 1. Add the correct equation and units when substituting where you forgot to on the Part Two to receive full points back. 2. Correct all problems you got wrong (Part One and Part Two) to receive half points back. 3. Hand them in to me in person during one of my free mods.

Like most Americans you weigh yourself on a bathroom scale in an elevator. If you have a mass of 75 kg, what will the scale read if the elevator is stationary? 735 N Elevator

What will the scale read if the elevator is moving at a constant velocity of 3 m/s? 735 N Elevator

If the elevator accelerates upward at 2 m/s^2 for 2 seconds what does the scale read during the 2 seconds of acceleration? 885 N Elevator

If the elevator accelerates downward at 2 m/s^2 for 2 seconds what does the scale read during the 2 seconds of acceleration? 585 N Elevator

Review sheet Homework

Bellringer – 2 mins to hand in What is the acceleration of a 75 kg person if the net force acting on them is -300 N? DO STOP WORK

Be able to solve stationary and moving elevator problems. Be able to calculate the force of air resistance. Know what tension is and use it to solve problems. Objectives

? ? ? Vector Quiz

If you failed the last test and did not complete corrections in order to raise your grade to a passing one you are one of the newest members of the science learning center! Can stay any day after school to catch up. Must stay Thursdays. You’re in the club until I think you’re good to go. Science Learning Center

Why do skydivers have a terminal velocity? Why do they need a parachute? Skydiving

What is a 80 kg skydiver’s drag force if his net acceleration is -2 m/s^2. Draw a free-body diagram of all the forces acting on the skydiver. Solve for the missing forces. Example

What is a 70 kg skydiver’s drag force if his net acceleration is -0. 5 m/s^2. Draw a free-body diagram of all the forces acting on the skydiver. Solve for the missing forces. You Try

What is the minimum acceleration a skydiver could have? What is the strongest drag force a 65 kg person could have? How does your velocity change the drag force? How does air density change the drag force? Maximum Drag Force

1. 2. What is the drag force on a 76 kg individual that is free-falling and has no acceleration? What is the drag force of a 100 kg food supply crate that is falling with zero net force? Checkpoint

http: //www. youtube. com/watch? v=rai. Frxb. Hx. V 0 Red Bull gives you wings

Lab Time

Parachute Lab

What is tension? ? Tension is simply a specific name for the force that a string or a rope exerts!! How many tensions can one rope have? Tension Force

Do tension forces push or pull? How do you know? Tension

Demos Nails and scales demo Tension and pulleys

You have a heavy crate of standard sized envelopes that has a mass of 50 kg. You decide the easiest way to move it is to pull it with a rope. If you put an acceleration on the box of 2. 5 m/s^2 what is the tension in the rope. (ignore friction) Two people are playing tug of war. If they each pull the rope with 50 N force in opposite directions what is the tension in the rope? Tension Examples

If two 5 kg masses hang from opposite sides of a rope around a pulley. What is the tension force in the rope? Tension examples

Find the tension force between two 1 kg boxes. The box on the left is being pulled with a force of 50 N and the box on the right is being pulled with a force of 80 N. Draw a free body diagram. Define the system you want to study. Solve for the missing forces. Back To Tension

When solving tension problems always start by looking at a system with the most known variables. Remember if objects or different parts of the system are physically connected they must have the same acceleration. Tension Problems

Find the tension force between two blocks that are hanging around a single fixed pulley. One block has a mass of 50 kg, the other has a mass of 80 kg. Draw a free body diagram. Define the system you want to study. Solve for the missing forces. Tension practice

Bellringer – 2 mins to hand in A 3, 000 kg Chevy is having a tug of war with a 2, 800 kg Ford. The Ford pulls with a force of 8, 000 N and the Chevy pulls with a force of 7, 500 N. What is the net force and the acceleration of the cars? DO STOP WORK

Be able to calculate the acceleration of a two mass system that is rotating around a pulley. Finish Lab Objectives

Today after school in room 122. Science Learning Center

The Atwood’s Machine: Invented by George Atwood in 1784 as a way to verify Newton’s Second Law of Motion F=ma Lab #7

Three blocks are each connected by separate strings, and are pulled along a frictionless surface. Box A is 4 kg, box B is 2 kg, and box c is 6 kg. If F is 36 N what is the acceleration of each box? What are the tension forces in each of the strings? Tension Example

Vector Quiz

Bellringer – 2 mins to hand in In your lab which mass rotates the pulley in the positive direction? DO STOP WORK

Be able to correctly label and calculate the normal force Figure out what variables effect the force of friction. Collect lab data Objectives

The Atwood’s Machine: Invented by George Atwood in 1784 as a way to verify Newton’s Second Law of Motion F=ma Lab #7

Vector Quiz

How would you label the force of: A table The floor The ground A chair The road The rug Labeling forces

The normal force is the perpendicular contact force that a surface exerts on another surface. Use free body diagrams to figure out what is going on. The Normal Force

The magnitude of the normal force is enough force to keep a system in equilibrium. Adding weights example The Normal Force

Examples

More Examples

Friction can come from a number of sources Heat Sound Air resistance Any kind of resistance Any unwanted loss of energy Friction Force

Though friction can come from a variety of sources there are only two types of friction that we are going to work with. Kinetic Friction Static Friction Types of Friction

Kinetic Friction Is exerted on one surface by another when the two surfaces rub against each other because one or both surfaces are moving against each other. Rubbing Friction Kinetic Friction

Static Friction Is the frictional force exerted on one surface by another when there is no motion between the two surfaces. Stationary Friction Increases to a point then becomes kinetic friction Static Friction

What factors do you think will change the friction force between two objects? Demo Would this be important to an athletic footwear manufacturer? BOOM! The labs never end! Friction Factors

http: //www. youtube. com/watch? v=c. Pp. Ox. Pl. CT Es https: //www. youtube. com/watch? v=Ek 5 Zyzn 3 Avw http: //www. youtube. com/watch? v=ibxtm. AVLa ag Foot Friction

Bellringer – 2 mins to hand in What is the normal force that a table exerts on a 5 kg textbook? DO STOP WORK

Figure out what variables control how much friction there is between two objects Finish Foot Friction Lab Objectives

The Atwood’s Machine: Staple it and hand it in Lab #7

What factors have you identified in your lab work that effect the magnitude of the friction force? Normal Force Type of surfaces that are rubbing Friction Factors

Kinetic Friction

What is the coefficient of kinetic friction between a 5 kg laptop and a table if the force of friction is 10 N? What is the kinetic friction force between waxed skis and snow if a 75 kg lady is skiing on level snow at constant velocity? Kinetic Friction example

Static Friction

What is the maximum static friction force between a 500 kg go kart with rubber tires and dry asphalt? What force is the minimum force required to push a 75 kg skier into motion on snow with freshly waxed skies? Static Friction example

Dynamics and Statics Review problems 1 -15 Homework

Label which part of the graph is static friction, kinetic friction, and at which point it starts to move. Bellringer

Be able to solve all kinds of friction problems Be able to solve force problems at an angle Objectives

Foot Friction Lab

Atwood’s Machine: Friction and Air Resistance Missing Labs…

Homework

Test next Monday and Tuesday Science Club on Thursday to catch-up/review for the test Is anyone interested in sending something into space? http: //space. 1337 arts. com/wpcontent/uploads/2009/09/1337 arts. Guide. pdf Updates

You push a 25 kg wooden box across a wooden floor at a constant speed of 1 m/s. The coefficient of kinetic friction is 0. 2. How large is the force that you exert on the box? Analyze and sketch Solve Evaluate Friction Practice

Gwen exerts a 36 N horizontal force as she pulls a 52 N sled across a cement sidewalk at constant speed. What is the coefficient of kinetic friction between the sidewalk and the metal sled runners? Ignore air resistance. More Practice

Mr. Ames is dragging a box full of books from his office to his car. The box and books together have a combined weight of 134 N. If the coefficient of static friction between the pavement and the box is 0. 55, how hard must Mr. Ames push horizontally on the box in order to start it moving? More Practice

Ricky Bobby is driving in his old Pontiac with rubber tires on dry concrete road. If he and his car have a combined weight of 10, 500 N what is his maximum static friction force before he starts to skid out and lose control of his vehicle? 9, 450 N What is the new force of friction if Ricky starts to skid? 7, 140 N Why is it so hard to regain control of your car once you lose it? Car Crash!!!

Why don’t magnets fall down? Magnets

Forces at an angle

Normal If Gary pushes the lawn mower at constant velocity with a force of 50 N down the handle. What is the magnitude of the force moving the mower forward? The handle is 50 degrees above the level ground. Fric. 32. 1 N N The Lawn Mower mg 38. 3 N 50

What angle is the most efficient to pull something? As the angle of the applied force on an object decreases from 90 degrees to 0 degrees what happens to the X component of the force vector? Angle Concepts

Tony is pulling a wagon at constant velocity. The wagon handle is 35 degrees above the level ground. If Tony pulls the handle with his 100 N force directed 35 degrees above the horizon what is the magnitude of the force in the direction of the motion? If the wagon weighs 150 N what is the normal force from the ground on the wagon? Angle Practice

If a 40 kg block is pulled across a frictionless floor at 30 degrees above the horizontal with a 75 N force what is the acceleration of the block in the horizontal direction? What is the original pull force if the Xcomponent is 25 N and the angle is 60 degrees? Checkpoint

1. 2. 3. What have you been doing since the last check to improve your grade? What will you do to improve you grade? What do you want your grade to be at the end of the quarter? Grades

Bellringer – 2 mins to hand in What is the force of kinetic friction between a 100 N steel plate sliding on copper surface at constant velocity? DO STOP WORK

Be able to solve dynamic problems at an angle. Objective

Test next week https: //twitter. com/Windsor_Physics Updates

Demo Video: http: //www. youtube. com/watch? v=k. Pf 8 FMJ 5 i. Js Inclined Plane

Inclined Plane

As the angle of an incline increases The normal force decreases The force from gravity down the incline increases The force from gravity into the incline decreases The frictional force decreases Inclined Plane

A 30 kg kid slides down a frictionless slide that is 30 degrees above the horizon. What is his force down the slide? 147. 15 N What is normal force from the slide? 254. 9 N Inclined Plane

A 2 kg rubber stopper is sliding down a 35 degree ice slide. What is the normal force acting on the stopper? 16. 1 N What is the friction force acting on the stopper? 2. 4 N What is the force of the stopper down the slope? 11. 3 N What is the net force on the stopper parallel to the slide? 8. 9 N What is the acceleration of the stopper down the slide? 4. 5 m/s^2 Inclined Plane

If a 1, 500 kg car is put in neutral on a 25 degree hill, how much force will it have as it rolls down? Ignore friction 6, 218. 8 N What is the normal force of a 50 kg boy that slides down a 15 degree frictionless snow slope? 473. 8 N What is that same boy’s force down the slope? 127. 0 N Checkpoint

Finish the rest of your Dynamics and Statics Packet Homework

Online demo https: //phet. colorado. edu/en/simulatio n/forces-1 d Force Demo

If the ramp is frictionless and m 1 is 35 kg and m 2 is 15 kg which way will the system move? Down the slope or up the slope? Incline plane

Make sure you review this homework assignment! Newton’s Laws HW

This is an outline of the concepts that you will be tested on. Make sure you understand every concept on here. You should also know what problems I might ask about each concept. How do these concepts relate to the labs and demonstrations we have done the past few weeks? Dynamics and Statics “Study Guide”

Bellringer – 2 mins to hand in DO STOP WORK

Be able to solve and statics or dynamics problem I throw at you! Objective

If you were there last week, I expect you there again today. Science Club

Begins Tuesday (11/4): 2: 35 to 3: 15 Physics Club: Our Journey to Space

Partner Up Gang!!! Station Activity

Bellringer – 2 mins to hand in DO STOP WORK

Bellringer – 2 mins to hand in What is the acceleration of a 10 kg block that is sliding down a frictionless slope of 30 degrees? DO STOP WORK

Be a dynamics and statics master. Objective

Begins Wednesday (11/5): 2: 35 to 3: 15 Physics Club: Our Journey to Space

Part 1: 25 multiple choice questions Part 2: 5 long answer questions Statics and Dynamics Test

Homework

Stations – Answers on website Sample Part Two Questions Study Guide Newton's HW Dynamics and Statics Review HW Chapters 4 and 5 Review