Motion, Newton's Laws

Resources: Glenbrook High School Physics; United States Air Force; CSU Stanislaus; University of Utah; Boston University Dept of Physics; Online Journey Through the Universe website; NASA

 

 

9.1 Forces and Motion

a. Discuss and apply Newton's laws (i.e.,first, second, third, and law of universal gravitation) Includes motion, acceleration, projectile motion, free fall, problem solving, Newton's laws of motion including momentum.
b. Define pressure and relate it to fluid flow and buoyancy (e.g., heart valves, atmospheric pressure)
c. Describe relationships among position, distance, displacement, speed, velocity, acceleration, and time, and perform simple calculations using these variables for both linear and circular motion- CLICK ON "a." ABOVE
d. Identify the separate forces that act on a body (e.g., gravity, pressure, tension/compression, normal force, friction) and describe the net force on the body
e. Construct and analyze simple vector and graphical representation of motion and forces (e.g. distance, speed and time)- CLICK ON "a." ABOVE
f. Identify fundamental forces, including gravity, nuclear forces, and electromagnetic forces (magnetic and electric), and explain their roles in nature, such as the role of gravity in maintaining the structure of the universe
g. Describe the causal relationships among heat, friction, and motion
h. Explain and calculate mechanical advantages for levers, pulleys, and inclined planes

 

 

Discuss and apply Newton's laws (i.e.,first, second, third, and law of universal gravitation)

Prior to Newton's laws students need to understand motion: Describing motion in words-(Be sure to study carefully each animation)

Introduction

Scalar and Vector Quantities

 

Displacement and Distance

Speed and Velocity

Look for the concepts of :
Instantaneous Speed
Average Velocity
Constant Velocity

Acceleration

Which way does the force of acceleration act (point) to cause an object to speed up, slow down or change direction?

Acceleration in Uniform Circular Motion

 

Describing Motion Using Drawings and Diagrams- (Be sure to study carefully each animation)

Introduction

 

 

 

Describing Motion Using Graphs

Position vs. Time Graphs

 

Velocity vs. Time Graphs

 

 

Free Fall and the Acceleration of Gravity- (Be sure to study carefully each animation)

Introduction

Acceleration of Gravity

Constant Acceleration

Representing Free Fall by Graphs

Example Calculations

Misconceptions of Free Fall

 

 

Projectile Motion- (Be sure to study carefully each animation)

What is Projectile Motion?

Characteristics of the Projectile's Pathway- Describing Projectiles with Numbers-Horizontal and Vertical Velocity
Describing Projectiles with Numbers- Horizontal and Vertical Displacement
Initial Velocity Components
Problem Solving-Horizontally Launched Projectiles
Problem Solving- Non-Horizontally Launched Projectiles- Advanced

 

Projectile Motion- Practice-USE APPLET 1 BELOW. IF NONFUNCTIONAL, USE APPLET 2. Click on yellow button to show applet 2 animation when the window opens- drag the applet at the edges to increase its width and height.

SET THE VELOCITY TO 70 m/s. Predict how the projectile path will look with different 1) angles the projectile is fired (start at 75 degrees and decrease the angle by 10 degrees (65, 55, 45, 35 and 25 degrees), each time pressing "fire", and 3) initial velocities of the projectile (return to the angle giving the greatest distance at 70 m/s and increase the velocity by 10 m/s (80, 90, and 100 m/s). NOW TRY THE EXPERIMENT. Write why your prediction was true or why it was false.

Finally, predict what a headwind (air resistance) will do to the distance traveled at all angles and initial velocities. Also predict what increasing the mass of the projectile will do to the distance traveled both without and with air resistance. IF YOU HAVE TO USE APPLET 2 YOU WON'T BE ABLE TO ADD AIR RESISTANCE AND MASS. Answer the questions above.

Run Projectile Motion Applet 1


Run Projectile Motion Applet 2

 

 

Kinematics Equations

Introduction

Problem Solving

Free Fall

Sample Problems

Problems: Kinematics Problems and Graphs

 

 

 

Identify the separate forces that act on a body (e.g., gravity, pressure, tension/compression, normal force, friction) and describe the net force on the body -in addition to the material above, from this point to the subject "Define Pressure and relate it to fluid flow and buoyancy" below, subjects deal with elements 9.1 a. c and e. .

 

Newton's First Law of Motion

An object will remain at rest or in uniform motion in a straight line unless acted upon by an external unbalanced force (LAW OF INERTIA)

Introduction

Inertia and Mass

State of Motion

Balanced and Unbalanced Forces- Introduction

The Meaning of Force

Types of Forces

Free-Body Diagrams

Determining Net Force

 

Newton's Second Law of Motion

F= ma (Force = mass times acceleration)

An unbalanced force acting on an object produces an acceleration OR an acceleration is evidence of an unbalanced force.

Introduction

Does an object in motion need an applied force to continue its motion? THE Big Misconception

Solving for Acceleration

Finding Individual Forces

Free Fall and Air Resistance

Mass and Weight- Review

 

Finding Acceleration with Two Applied Forces

Addition of Forces

Resolution of Forces

Equilibrium and Statics

Net Force Problems (again)

Inclined Planes

 

Test your understanding of the relationship between Force and Acceleration... Click on down arrow to see answer.

 

Combining both Newton's First and Second Law we have the most powerful knowledge to keep safe as we drive on today's highways or... if we choose to ignore the concepts... accident, injury and possibly even death.
  • After you click on the link below, set the speed of the cars to 80 miles per hour.

    Measure how long your own car at home is in feet and set the distance between cars to that number. Look for "d=" and type in the number and change the m (meters) to ft (feet). in the graphic below d is set to 12.0 m (meters). Type in the length of your car where the 12.0 is and click on the down arrow and change m to ft.

    When you press the reset button (see picture to the left) (1), cars travel from left to right with the yellow car in the lead. You have already changed the speed of your cars to 80 ) and changed m/s to mi/h by using the down arrow. You have already entered the length of your car and changed m to ft . This length becomes the distance between each car... this is your starting place.

    The coefficient of friction between your tires and the road (leave as is). However, consider how stopping distances may change on wet highways, ice, snow... etc.

    You will watch the lead car (yellow) until it turns RED. and then IMMEDIATELY CLICK ANYWHERE IN THE AREA OF THE PICTURE TO THE LEFT WHERE THE RED LETTERS ARE.

    If ALL the cars have stopped without crashing, then you are traveling just the right distance from the car in front of you. A CRASH OCCURS WHEN ONE OR MORE OF THE CARS SHOW AS A RED-LINED BOX, FILLED ONLY BY THE COLOR OF THE BACKGROUND.

    IF ANY of the cars crash, you are following too close. IF THIS IS THE CASE, YOU PROCEED IN TWO STEPS. 1) First, decrease the speed by 10 mi/h increments, keeping the distance the same. Report the lowest speed where you had no accidents.

    2) Secondly, keeping the speed at 80 mi/h, increase your distance between cars. For example, in the case to the left your car was 12 feet long. Next try 24 feet separation... next 36 feet... etc. until you have NO accidents at all. Obviously, if your car is 8 feet long, you start at 8 feet and increase by increments of 8. Report the distance where there are no accidents at 80 mi/h

    How many OF YOUR CAR LENGTHS will you have to have between you and the car ahead of you need to be there to keep safe on the highway. How will your own driving habits change?

    Click here to find out how we can stay safe while we drive

 

Newton's Third Law of Motion

For every action, there is an equal and opposite reaction. Forces always occur in pairs and ACT ON DIFFERENT OBJECTS.

Introduction

Action and Reaction Force Pairs

 

Newton's Law of Gravitation

Introduction- also includes concepts of center of gravity (not required)

 

Momentum is the force of motion

A train traveling at 10 meters per second has a much greater momentum (force of motion) than does a housefly traveling at the same velocity. (Momentum is a vector as well as force, acceleration and velocity.)

Linear Momentum (p = mv)

Law of Conservation of Linear Motion- When two objects in linear motion collide, the "post-collision" momentum of the two objects is the same as the "pre-collision" momentum of both objects. In otherwords, the total linear momentum of an isolated system is the same if there is no external unbalanced force acting on the system.

2D Collisions

Air Track

 

Angular Momentum- Angular momentum arises when an object goes around a path around a fixed point. L= mvr

Law of Conservation of Angular Momentum- In the case of a planet in its elliptical orbit does is at a different distance from the fixed point. It's velocity may change slightly also. Therefore at any two points in its orbit, mv1r1 = mv2r2 .

Momentum

Introduction

Momentum and Impulse Connection

Real World Application

Newton's Third Law (again)

Momentum Conservation Principle

Isolated Systems

Problem Solving

Using Equations To Guide Our Thinking

 

Define pressure and relate it to fluid flow and buoyancy (e.g., heart valves, atmospheric pressure)

Air Pressure

Blood Pressure/Lowering High Blood Pressure

Fluid Flow

Buoyancy

Fluid flow and heart valves:

Animation of the beating heart, the force that produces the pressure to flow through the heart valves, veins and arteries.

Animation of beating heart with ejecting blood

 

 

Identify fundamental forces, including gravity, nuclear forces, and electromagnetic forces (magnetic and electric), and explain their roles in nature, such as the role of gravity in maintaining the structure of the universe

Introduction- the fundamental forces of nature-Introduction to the theories of Unification....

 

Nuclear forces (strong interaction) holds the atoms together. Without this there would be

It is very strong but its effects are short-ranged

 

Electromagnetic forces are weaker than the strong force but are very long ranged. It influences (attraction or repulsion) of other charged particles. Without electromagnetic forces

For additional information click here

The weak force is responsible for radioactive decay and neutrino interactions. It has a very short range and, as its name indicates, it is very weak. Without radioactivity

 

The gravitational force is weak, but very long ranged. Furthermore, it is always attractive, and acts between any two pieces of matter in the Universe since mass is its source. Gravitational forces

 

 

Describe the causal relationships among heat, friction, and motion

We can define friction as the resistance to the movement of one body in relation to another body with which it is in contact. For example if we try to slide a wooden block across a table then friction acts in the opposite direction to the movement of the brick. The amount of friction will depend upon the nature of the two surfaces in contact with each other. The energy of movement is conserved. Where friction exists, part of the energy of movement is transferred to heat produced on the objects that move over another. That is why your tires become warm when traveling at 80 miles per hour on a cold winter's day.

If both the block and the table are highly polished (smooth) then there will be less friction than if the surfaces were rough and also the amount of heat produced would be less. If we were to reduce all friction between the tires of car and the road (like on ice), the tires would stay cool, but we would get mad as we drove off the road, unable to turn when the road turned. Many accidents would be caused as a result.

If we try to slide one object over another the irregularities in the surfaces of the two objects (their degree of roughness) causes resistance to the movement and we have friction. The energy lost forms heat. If we were rolling one object over another the friction (and heat) still arises because of imperfections in the surfaces. Friction then is a measure of the force pressing the two objects together.

 

How friction of the movement of the continental plates on earth produces heat- example: the heat melts the rocks and volcanoes are formed.

 

 

Explain and calculate mechanical advantages for levers, pulleys, and inclined planes

Concepts of Simple Machines

Mechanical advantage for levers, pulleys and inclined planes

 

Details of other physics concepts

Heat Transfer and Thermodyanmics

 

 


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