S7 - Q4 - Unit 1 Review
Forces and Interactions + Critical Thinking
Learning Objectives
Interpret position-time graphs to determine speed, direction, and motion patterns
Apply Newton's three laws of motion to explain real-world phenomena
Explain the relationship between magnetism and electricity, including electromagnets
Identify the 8 logical fallacies by name and definition
Detect logical fallacies in real-world scenarios
Apply the 3-question defense strategy to evaluate claims
Section 1: Graphing Motion Review
~2 minutesGraphing Motion Review
Position-time graphs show an object's position (y-axis) versus time (x-axis). Everything you need to know about an object's motion is encoded in the shape and slope of the line.
- The SLOPE of the line = SPEED (rise over run = change in position / change in time)
• Steeper line = FASTER speed; gentle slope = slower speed
• Flat horizontal line = object at REST (not moving)
• Straight line = CONSTANT speed; curved line = CHANGING speed (acceleration)
• Line going UP = moving AWAY from starting point; line going DOWN = moving BACK toward start
• Where two lines CROSS = two objects at the SAME POSITION at the SAME TIME
Speed Formula
speed = distance / time (s = d/t)
Example: If an object moves 30 meters in 10 seconds, speed = 30/10 = 3 m/s
Position: an object's location relative to a reference point. Speed: the distance an object travels per unit of time. Velocity: speed in a specific direction. Acceleration: a change in speed or direction over time. Constant speed: equal distances covered in equal time intervals (straight line on a graph). At rest: no change in position over time (horizontal line on a graph).
Graphing Motion Questions
On a position-time graph, what does the slope of the line represent?
A flat horizontal line on a position-time graph means the object is moving at a constant speed.
An object travels 60 meters in 20 seconds at constant speed. What is its speed?
On a position-time graph, Line A is steeper than Line B. Which statement is correct?
A curved line on a position-time graph indicates the object is accelerating.
Two lines cross on a position-time graph at time = 5 seconds. What does this mean?
An object moves 100 meters in 25 seconds. Its speed is ______ m/s.
On a position-time graph, a line that slopes downward means the object is:
Object X has a position-time graph that is a straight line going up steeply. Object Y has a curved line that starts flat and gets steeper. At the beginning of the graph, which object is moving faster?
If a position-time graph shows a straight line with a positive slope, the object is moving at a changing speed.
Section 2: Forces and Newton's Laws Review
~2 minutesForces and Newton's Laws
What Is a Force?
A force is a push or pull on an object, measured in Newtons (N). Forces have both size and direction, making them vectors.
- Net Force: the combined effect of all forces acting on an object
• Balanced forces: net force = 0, NO change in motion (object stays still or keeps moving at constant speed)
• Unbalanced forces: net force is NOT 0, causes ACCELERATION (speeding up, slowing down, or changing direction)
Newton's First Law (Law of Inertia)
An object at rest stays at rest. An object in motion stays in motion at the same speed and direction. UNLESS an unbalanced force acts on it.
Inertia = resistance to change in motion. More mass = more inertia.
Newton's Second Law (F = m x a)
Force = mass times acceleration.
- More force = more acceleration
• More mass = less acceleration for the same force
• Units: Force in Newtons, mass in kg, acceleration in m/s2
Example: If a 10 kg object has a net force of 50 N, acceleration = F/m = 50/10 = 5 m/s2
Newton's Third Law (Action-Reaction)
For every action force, there is an equal and opposite reaction force. The two forces act on DIFFERENT objects.
Example: You push on a wall, the wall pushes back on you with equal force.
1st Law: Objects are lazy (inertia). They keep doing what they are doing unless forced to change. 2nd Law: F = m x a. A bigger push makes things go faster. More mass makes things harder to move. 3rd Law: Every push gets a pushback. Action and reaction are always equal and opposite, but they act on different objects.
Forces and Newton's Laws Questions
What is the unit used to measure force?
When balanced forces act on a moving object, the object slows down and stops.
A soccer ball is sitting on the field. A player kicks it. Which of Newton's Laws best explains why the ball starts moving?
A 5 kg box is pushed with a net force of 20 N. What is its acceleration?
Newton's Second Law states that Force = ______ x ______.
When you push against a wall, the wall pushes back on you with equal force. This is an example of Newton's:
A 2 kg ball and a 10 kg ball are pushed with the same force. Which ball will have greater acceleration?
Newton's Third Law says that action and reaction forces act on the same object.
Which of the following are examples of unbalanced forces? (Select all that apply)
Select all that apply.
A net force of 30 N acts on an object, causing it to accelerate at 6 m/s2. What is the mass of the object?
A passenger in a car lurches forward when the driver hits the brakes. Which law explains this?
Match each scenario to the Newton's Law it best demonstrates.
Section 3: Magnetism and Electricity Review
~2 minutesMagnetism and Electricity
Magnets and Magnetic Fields
- A magnetic field is the invisible region around a magnet where magnetic force acts
• Every magnet has a North and South pole
• Opposite poles ATTRACT (N-S), like poles REPEL (N-N or S-S)
• Breaking a magnet in half creates TWO complete magnets, each with N and S poles
The Discovery That Changed Everything
Hans Christian Oersted (1820) discovered that electric current creates a magnetic field. This showed electricity and magnetism are connected.
Electromagnets
An electromagnet is a coil of wire wrapped around an iron core, with electric current flowing through it.
Advantages over permanent magnets: 1. Can be turned ON and OFF 2. Strength can be adjusted by changing current or number of coils 3. Poles can be REVERSED by reversing current direction
Applications: electric motors, generators, speakers, MRI machines, maglev trains, junkyard cranes
Key discovery: Electricity produces magnetism, and magnetism can produce electricity (generators).
Magnetic field: the invisible region around a magnet where magnetic force acts. Poles: the north (N) and south (S) ends of a magnet. Attract: what opposite poles do (pull toward each other). Repel: what like poles do (push away from each other). Oersted: the scientist who discovered that electric current creates a magnetic field. Electromagnet: a magnet made by running current through wire coils around an iron core. Electromagnetism: the connection between electricity and magnetism.
Magnetism and Electricity Questions
What happens when two north poles of magnets are brought together?
If you break a magnet in half, you get one piece with only a north pole and one with only a south pole.
Which scientist discovered that electric current creates a magnetic field?
Which of the following are advantages of electromagnets over permanent magnets? (Select all that apply)
Select all that apply.
How can you make an electromagnet stronger?
A student builds an electromagnet and wants to reverse its poles. What should the student do?
Section 4: Critical Thinking and Logical Fallacies Review
~2 minutesLogical Fallacies Quick Reference
| Fallacy | What It Does | Example |
|---|---|---|
| Ad Hominem | Attacks the person, not the argument | "You failed math, so your opinion on the budget is worthless" |
| Straw Man | Distorts the argument into an extreme version | "You want less homework? So you want students to never learn anything?" |
| Red Herring | Changes the subject to distract | "Why worry about pollution when there are potholes on the roads?" |
| Bandwagon | Claims it is true because everyone does it | "Everyone is buying this phone, so it must be the best" |
| False Dilemma | Presents only two options when more exist | "Either you agree with me, or you do not care about the environment" |
| Slippery Slope | Claims one step leads to disaster without evidence | "If we allow phones in class, students will never read books again" |
| Appeal to Authority | Uses a famous person without relevant expertise | "This celebrity says the product works, so it must" |
When you hear a claim, ask these three questions: (1) What is the actual claim? (2) What evidence supports it? (3) Is the reasoning valid, or does it contain a fallacy? If you cannot get clear answers to all three, be skeptical.
Critical Thinking Questions
Which logical fallacy presents only two options when more actually exist?
Match each statement to the logical fallacy it demonstrates.
"If we allow students to retake one test, soon they will want to retake every assignment, and eventually no one will try on the first attempt." Which fallacy is this?
"My favorite singer says this diet works great!" Which fallacy is this?
"We should discuss the school dress code." "Why are we talking about clothes when the cafeteria food is so bad?" Which fallacy is this?
A classmate says: "You want to add more vegetables to the lunch menu? I guess you want to take away everything fun and make us all miserable." Which TWO fallacies are present in this statement?
Select all that apply.
What is the SECOND question in the 3-question defense strategy?