K

Energy Honors Intro to Physics Final Exam Review Notes

Energy Honors Intro to Physics Final Exam Review

General Review Guidelines

  • This review guide provides vocabulary and concepts for studying the "Big Ideas."

  • It includes extra practice questions and problems (with answers in a separate document).

  • The midterm exam will be similar to unit tests and quizzes, but longer.

  • To prepare:

    • Review textbook presentations, shell notes, and math problem worksheets.

Covered Chapters/Sections

  • Chapter 2: Mechanical Equilibrium (2.1-2.4)

  • Chapter 3: Newton’s 1st Law: ALL

  • Chapter 4: Linear Motion: ALL (speed, velocity, and acceleration)

  • Chapter 6: Newton’s 2nd Law: 6.1-6.4 and 6.6-6.7 (excluding pressure)

  • Chapter 7: Newton’s 3rd Law: 7.1 – 7.4, 7.7

  • Chapter 8: Momentum: 8.1 - 8.5

  • Chapter 9: Energy: 9.1-9.9

Practice Resources

  • DO Google Form Practice Quizzes again.

  • DO Concept Builders again (log out and do as a guest).

Formulas and Problem Solving

  • Understand how changes in variables affect other variables in the formulas.

  • Be familiar with all formulas and units.

  • Be able to solve problems (formulas will be provided on the exam).

  • Review all homework assignments and labs.

Lesson Plan Links

  • Find links to lesson plan documents for each unit.

  • All Google Forms Practice Quizzes are reset.

  • Re-do Concept Builders as a guest by logging out of Physics Classroom.

    • Forces and Mechanical Equilibrium (MG)

    • Newton's 1st AND 3rd Law of Motion and Mass vs Weight

    • 2nd Law of Motion: Unbalanced Forces (Accelerated Motion)

    • Momentum

Newton’s Laws of Motion, Constant Motion, and Mechanical Equilibrium

Main Idea

  • For an object to be in constant motion, it must be in mechanical equilibrium.

  • This is formally presented as Newton’s 1st Law of Motion.

Key Definitions

  • Constant motion (at rest and moving)

  • Mechanical equilibrium

  • Newton’s First Law (including direction of motion)

  • Distance, Average Speed, Average Velocity, and Acceleration

  • Scalar and vector

Word Problems

  1. Average speed of a firetruck that travels 3,000m in 10 min?

  2. Average walking speed in m/s if you go 1 m in ½ sec?

  3. How far will you travel (in km) in a half hour moving at 10km/hr?

  4. How far (in meters) will you travel if you maintain an average speed of 10m/s for 40 sec?

Constant Motion and Balanced Forces

  • Constant motion implies balanced forces.

  • Mechanical equilibrium: Forces are balanced: \sum F = 0N and a = 0m/s^2

Calculating Net Force

  1. 2N right and 3N right = 5N right

  2. 2 N right and 7 N left = 5 N left

  3. Maximum possible resultant of 8N and 7N? 15N

  4. Minimum possible resultant of 8N and 7N? 1N

Force Diagrams

  1. Identify which force diagram shows an object moving with constant speed.

  2. If an object is moving at speed in a _ path, it must be in a state of .

  3. If an object is standing still, the sum of the forces in the x-direction must be _ and the sum of the forces in the y-direction must be __.

  4. A ball at rest on a table weighs 5 N, the net force on the ball is __.

  5. The support force is equal to ____N. 5N

  6. The reaction force of the ball pushing on the table is… “ pushing on __ ”. Table pushing on Ball

  7. Two strong men each pull on a rope with 200N of force; the tension in the rope is 200N.

  8. A wagon is pulled with a force of 100N and does not move, the frictional force must be equal to 100N.

  9. A wagon is pulled with a 250 N force and moves with constant speed, what must the value of the frictional force be? 250N

Class Activity Review

  • Review examples from class activities (like the tablecloth trick).

  1. Why didn’t the dishes move? Inertia

  2. Why did Barbie/Bart fall out without his/her seatbelt? Inertia

  3. What was the path of the marble inside the circle when a piece of that puzzle was removed? What path will an object in motion take if there is no force acting on it? The marble will travel in a straight line tangent to the circle at the point of release.

Mass vs. Weight

  • Define and know the difference between mass (inertia) and weight.

  1. If you double an object’s mass, what else will double?
    a. Inertia
    d. Weight

  2. What is the weight of a 6kg box? W = mg = 6kg * 10m/s^2 = 60N

  3. What is the mass of an object that weighs 200N? m = W/g = 200N / 10m/s^2 = 20kg

  4. If I take a 5kg box to the moon, what will decrease? Weight

Main Idea: Accelerated Motion and Unbalanced Forces (Newton’s 2nd Law)

  • F = m*a AND a = \frac{\Delta V}{t}

  • If an object’s motion is changing (accelerating), the sum of the forces is NOT equal to zero.

Free Fall

  • Only affected by the force of gravity; g = 10m/s^2 (acceleration due to gravity).

  • All objects, regardless of their mass, will accelerate at the same rate.

  1. For an object thrown straight up in the air, on the way up, its speed decreases and its acceleration remains the same. At the top of the toss, the speed of the ball is 0 and the acceleration is 10m/s². (g = 10m/s^2)

  2. An object thrown straight down compared to the same object dropped from rest: Which object has the greater acceleration (same = 10m/s^2). Which one will hit the ground first? The one thrown down

  3. At what rate does the speed of a freely falling object increase? 10m/s^2

Acceleration Calculations

  • g = 10m/s^2

  • F = m*a AND a = \frac{\Delta V}{t}

  1. A car accelerates from rest to a speed of 20 m/s in 4 sec
    a. Acceleration? = a = \frac{20m/s}{4s} = 5m/s^2
    b. How far did it go in 4 sec?
    c. How fast is the car going at the end of the 4th second? 20 m/s

  2. An apple is dropped from rest, what is its speed at the end of the 5nd second? v = gt = (10m/s^2)(5s) = 50 m/s

  3. How far will it fall in 5 seconds? d = \frac{1}{2}gt^2 = \frac{1}{2}(10m/s^2)(5s)^2 = 125m

  4. A 150N force pulls a 14 kg object, initially at rest, to the right, while an 80 N force of friction also acts on the object.
    a. How far will it go in 10 sec (WHICH EQUATION IS HOW FAR?)
    b. How fast is it going after 10 sec (WHICH EQUATION TELLS YOU HOW FAST?)

  5. A 5N bowling ball is dropped from rest; what is the net force on the object? 5N

  6. A 100N ball and an 80N ball are both dropped from a building and experience air resistance as they fall. Which will hit the ground first, or will they both hit at the same time? The 100N ball

  7. An object is dropped and experiences significant air resistance as the object falls, its speed increases. It's acceleration decreases. And it’s net force decreases.

  8. For a constant mass object, a constant net force on the object will produce constant acceleration!

  9. Draw a force diagram of an object experiencing terminal velocity. What is the acceleration of the object at this point? What about its net force? And its velocity?

Terminal Velocity

  • Understand how a skydiver reaches terminal velocity due to air resistance.

Newton’s Third Law

  • Every action has an equal and opposite reaction.

  1. Apple at rest on a table, apple’s weight pushes down on the table, the reaction force is the table pushing up on the apple.

  2. The action force of a person's sitting in a chair is the Earth pulling on the person, the reaction force is the person pulling up on the Earth.

  3. Which exerts a greater force when a gun fires a bullet? The forces are equal: the force of the gun on the bullet is equal to the force of the bullet on the gun.

  4. Why does the bullet accelerate more? Because it has less mass.

  5. Forces always occur in pairs.

  6. Recognize the difference between an action/reaction force pair that are equal and two forces that are equal when in equilibrium.

Energy

Main Idea

  • Energy is conserved: the total amount stays the same.

  • W = F*d = \Delta Energy

  • Work can change potential energy by lifting it, or work can accelerate an object to change its kinetic energy.

  • Potential energy (PE) = mgh (energy due to position)

  • Kinetic ENERGY (KE) = \frac{1}{2}mv^2 (energy of motion)

  • Mechanical Energy = PE + KE

  • Use Energy to solve falling object problems.

  • PE_{el} = \frac{1}{2}kx^2 (elastic PE)

Power

  • Rate that work is done (Unit: WATT).

  • P = \frac{W}{t}

Simple Machines

  • Work input = Work output

  • (force × distance) input = (force × distance) output

  1. How much work is done to lift a 5kg box to a height of 12m? W = mgh = (5kg)(10m/s^2)(12m) = 600J

  2. How much work is done to accelerate a 1000kg car from rest to a speed of 15m/s? W = KE = \frac{1}{2}mv^2 = (0.5)(1000kg)(15m/s)^2 = 112500J

  3. How much work is done by a 7N force that pushes a box for 3m? W = Fd = (7N)(3m) = 21J

  4. How much power is used in climbing a 7m ladder in 30 sec by a 60 kg worker? P = \frac{W}{t} = (\frac{mgh}{t}) = \frac{(60kg)(10m/s^2)(7m)}{(30s)} = 140 Watts

  5. How much kinetic energy does a 150N linebacker moving at 4m/s have?

  6. How much potential energy does a 0.25N pendulum bob have if it is pulled back 0.5m?

  7. As a pendulum swings from its highest point to the bottom, its PE decreases and KE increases and total energy remains the same.

  8. A car traveling at 25 mph skids to a stop in 20m with its brakes locked. How far would it skid if it doubled? Tripled? It’s speed

  9. You use a big lever to lift a heavy box. If you push down with 20N of force and move it a distance of 2m, on the other end, the 800N box will be lifted. How high? __

  10. Using the diagram below. The height relative to the ground at position W is 25m. Position X is at 0m. Position Y is at 10 m and position Z is at 3m. The mass of the roller coaster car is 150kg. Assume the car is momentarily at rest at position W and there are no losses due to friction.
    a. What is the work done by the motor to life the car to position W?
    b. If it takes 45 sec to lift the car to position W, how much power is expended?
    c. Determine the speed at position X?
    d. Determine the speed at position Z?

Momentum

The Big Idea

  • Momentum is conserved for all collisions as long as external forces don’t interfere.

  • Momentum (p) is the mass of the object multiplied by its velocity. (p = m*v)

  • Impulse Changes Momentum: The change in momentum depends on the force that acts and the length of time it acts.

  • The quantity force x time interval is called impulse. In short-hand notation, impulse = F*t.

  • The greater the impulse exerted on something, the greater will be the change in momentum. The exact relationship is impulse = change in momentum or Ft = \Delta(mv).

  • Bouncing: The impulse required to bring an object to a stop and then to “throw it back again” is greater than the impulse required merely to bring the object to a stop.

  • Collisions: Whenever objects collide in the absence of external forces, the net momentum of both objects before the collision equals the net momentum of both objects after the collision.

  • To review… See recent Class problems and Concept Builders

Case Studies

  • Especially the Case Studies “bouncing” and know how to calculate:

    • Change in velocity

    • Change in Momentum

    • Impulse

    • Force

53.