Unit 1 Test - Review Guide
UNIT FOCUS
Understand and apply Newton's Laws of Motion, analyze forces using free-body diagrams, solve problems involving friction, inclined planes, and circular motion, and apply concepts to real-world situations.
KEY CONCEPTS TO STUDY
1. Newton's Laws of Motion
- 1st Law (Inertia): Objects remain at rest or in unifrom motion unless acted upon by a net force.
- 2nd Law: Net force = mass x acceleration (\(F_{net}=ma\))
- 3rd Law: For every action, there is an equal and opposite reaction.
2. Free-Body Diagrams (FBDs)
- Practice drawing FBDs for objects on horizontal and inclined planes.
- Include all forces: gravity (\(F_g\)), normal force (\(F_N\)), applied force (\(F_a\)), friction (\(F_f\)), tension (\(T\)), etc.
3. Types of Forces
- Gravitaional Force: \(F_g=mg\)
- Normal force: Perpendicular to the surface
- Friction:
- Static: \( F_s \leq \mu_sF_N \)
- Kinetic: \( F_k \leq \mu_kF_N \)
- Tension and Applied Forces
4. Inclined Planes
- Break gravity into components:
- Along the incline: \( F_{||}=mgsin \theta \)
- Perpendicular to incline: \( F_{⊥}=mgcos \theta \)
- Normal force and friction depend on angle.
5. Circular Motion
- Objects moving in a circle at constant speed have centripetal acceleration:
- \( a_c= \frac{v^2}{r} \)
- \( F_c= \frac{mv^2}{r} \)
- Centripetal force is not a new force; it's the result of another (tension, gravity, friction).
6. Friction
- Know how to calculate and compare static and kinetic friction.
- Understand the role of friction in circular motion and on ramps.
PROBLEM-SOLVING SKILLS
- Analyzing forces in 1D and 2D motion
- Applying Newton's laws to real-world systems (e.g., ramps, elevators, rope tension)
- Solving for unknowns: acceleration, force, friction, velocity
- Interpreting FBDs and breaking vectors into components
- Applying concepts to conceptual and numerical equations
COMMUNICATION TIPS
- Clearly explain concepts using scientific language
- Justify answers logically (e.g., why friction increases or decreases)
- Use diagrams to support explanations
- Practice full-sentence explanations for multi-step problems
SAMPLE REVIEW QUESTIONS
1. A 10.0 kg box is pulled across a floor with a force of 40 N at \(25^o\) above the horizontal. The coefficient of kinetic friction is 0.3. What is the box's acceleration?
2. A 1200 kg car rounds a curve of radius 60 m at a speed of 18 m/s. Will the car skid if \( \mu_s=0.25 \)?
3. Draw a complete FBD for a sled being pulled uphill with a rope. Include all force components.
4. In your own words, describe the motion of an object that experiences a net force of zero.
5. Compare and contrast static and kinetic friction with real-life examples.
6. You are helping to design a driver education course. You are asked to explain how Newton's three laws apply when a car:
- starts moving from rest,
- travels at a constant speed, and
- comes to a stop.
Write a short paragraph explaining how each of Newton's three laws of motion is demonstrated during these phases of motion. Be sure to use proper terminology and provide real-world reasoning.
Tip: One paragraph per law is a good structure. Use terms like "net force", "acceleration", "inertia", and "action-reaction" as appropriate.
TEST DAY REMINDERS
- Make sure to have a scientific calculator
- You may use your notes and handouts (open book)
- Show all work for calculation questions
- Label diagrams and state final answers clearly