Comella science

Physics S1 Study Guide

Physical Science Study Guide

Complete Edition: Units 1-5

Energy, Motion, and Forces


Table of Contents

Unit 1: Energy Storage & Transfer

  • • Key Concepts
  • • Representational Tools
  • • Practice Questions

Unit 2: Constant Velocity

  • • Key Concepts
  • • Graphs & Equations
  • • Practice Questions

Unit 3: Uniform Acceleration

  • • Key Concepts
  • • Kinematic Equations
  • • Practice Questions

Unit 4: Balanced Forces

  • • Force Diagrams
  • • Key Equations
  • • Practice Questions

Unit 5: Unbalanced Forces

  • • Newton’s Laws
  • • Energy Connections
  • • Practice Questions

Additional Resources

  • • Study Tips
  • • Answer Key

Unit 1: Qualitative Models of Energy Storage and Transfer

Key Concepts

  • Energy is the ability to cause a change
  • Energy Storage Modes:
    • Kinetic (Ek): energy in moving objects
    • Thermal (Eth): energy in collection of moving particles (temperature)
    • Gravitational (Eg): energy in gravitational field
    • Elastic (Eel): energy in springs or stretchy things
    • Chemical (Ech): energy in chemical bonding
    • Physical (Eph): energy in electric field due to physical state
  • Energy Transfer Mechanisms:
    • Working (W): energy transfer by forces acting across distance
    • Heating (Q): energy transfer due to temperature differences
    • Radiating (R): energy transfer by electromagnetic waves
  • Systems: Can be open (energy enters/leaves) or closed (energy stays within)
  • Conservation of Energy: Energy is neither created nor destroyed, only transferred or transformed

Representational Tools

  • System Schema: Shows objects in system, surroundings, and interactions. Draw a dotted line around your system!
  • Energy Pie Charts: Qualitative representation of energy storage at different times. Size of pie = total energy; slices = storage modes
  • Energy Bar Charts (Energy Flow Diagrams): Shows energy storage AND transfer mechanisms with arrows

Key Equation

ΔEsystem = W + Q + R = ΔEg + ΔEel + ΔEph + ΔEchem + ΔEk + ΔEth

Energy change in system = Energy transfers = Sum of all energy storage changes

What You Should Be Able To Do

  • Draw system schemas identifying objects, boundaries, and interactions
  • Create energy pie charts showing initial and final energy storage
  • Identify how energy is stored in different scenarios
  • Describe how energy transfers between storage modes
  • Apply energy concepts to engineering design problems

Unit 1 Practice Questions

  1. Energy Storage: A spring-loaded toy car is compressed and released. It rolls across a table and eventually stops. Draw energy pie charts for: (a) when compressed, (b) just after release, (c) moving at top speed, (d) when stopped.
  2. System Schema: For a book falling from a shelf to the floor, draw a system schema. Include the book, Earth, and gravitational field in your system.
  3. Energy Transfer: When you rub your hands together, they get warm. What type of energy transfer is occurring? What energy storage modes are involved?
  4. Conservation: Two identical balls roll down ramps of different angles but the same height. Which has more kinetic energy at the bottom? Explain using energy conservation.

Unit 2: Constant Velocity Motion

Key Concepts

  • Position (x): Location relative to a reference point (origin)
  • Displacement (Δx): Change in position (can be positive or negative)
  • Velocity (v): Rate of change of position (vector – has direction)
  • Speed: Magnitude of velocity (always positive, no direction)
  • Constant velocity: Equal displacements in equal time intervals
  • Objects moving at constant velocity have kinetic energy (Ek)

Graphical Representations

  • Position-Time (x-t) graphs:
    • Slope = velocity
    • Straight line for constant velocity
    • Steeper slope = faster motion
  • Velocity-Time (v-t) graphs:
    • Area under curve = displacement
    • Horizontal line for constant velocity
  • Motion Maps:
    • Dots show position at equal time intervals
    • Equal spacing = constant velocity
    • Arrows show velocity direction

Key Equations

Average velocity: v̄ = Δx/Δt

Position equation: x = x₀ + vt (when ti = 0)

General form: xf = xi + v(tf – ti)

What You Should Be Able To Do

  • Create and interpret position-time and velocity-time graphs
  • Draw motion maps for constant velocity motion
  • Calculate velocity from position-time data
  • Convert between verbal descriptions, graphs, equations, and motion maps
  • Identify when objects have constant velocity from graphs or descriptions

Unit 2 Practice Questions

  1. Graphing: An object moves from position 0m to 10m in 5 seconds at constant velocity. Sketch both the position-time and velocity-time graphs.
  2. Velocity Calculation: A car travels 150 meters in 30 seconds. What is its velocity?
  3. Motion Maps: Draw a motion map for a bicycle moving at 5 m/s to the right for 4 seconds. Show at least 5 dots.
  4. Displacement vs Distance: You walk 3 meters east, then 4 meters west. What is your (a) distance traveled? (b) displacement?
  5. Graph Interpretation: If a position-time graph is a straight line with positive slope, what can you say about the object’s velocity?
  6. Area Under Curve: On a velocity-time graph, a horizontal line at 8 m/s extends from t = 0 to t = 6s. What is the displacement?

Unit 3: Uniform Acceleration

Key Concepts

  • Acceleration (a): Rate of change of velocity
  • Uniform acceleration: Velocity changes by equal amounts in equal time intervals
  • Instantaneous velocity: Slope of tangent line on x-t graph (velocity at a specific moment)
  • Average velocity (uniformly accelerated): v̄ = (vi + vf)/2
  • Important: Positive acceleration does NOT always mean speeding up – depends on direction!
  • Free fall acceleration: g ≈ 9.8 m/s² or 10 m/s² (downward near Earth’s surface)

Graphical Representations

  • Position-Time: Curved (parabolic) for uniform acceleration
  • Velocity-Time: Straight line, slope = acceleration
  • Acceleration-Time: Horizontal line for uniform acceleration
  • Motion Maps:
    • Dots get farther apart (speeding up) or closer together (slowing down)
    • Velocity vectors change length
    • Acceleration vectors stay constant
  • Area under v-t graph = displacement

Key Equations

Acceleration: a = Δv/Δt = (vf – vi)/(tf – ti)

Velocity: vf = vi + a(tf – ti) or vf = vi + at

Position: xf = xi + vit + ½at²

Displacement: Δx = vit + ½a(Δt)²

Gravitational energy: ΔEg = mgΔh

What You Should Be Able To Do

  • Distinguish between average and instantaneous velocity
  • Draw and interpret x-t, v-t, and a-t graphs for accelerated motion
  • Calculate acceleration from velocity-time data
  • Use kinematic equations to solve motion problems
  • Create motion maps showing velocity and acceleration vectors
  • Analyze energy transfers between Eg and Ek for objects on ramps or in free fall

Unit 3 Practice Questions

  1. Acceleration: A car goes from 0 m/s to 25 m/s in 10 seconds. What is its acceleration?
  2. Instantaneous Velocity: How do you find instantaneous velocity from a position-time graph?
  3. Free Fall: A ball is dropped from rest. How far does it fall in 2 seconds? (Use g = 10 m/s²)
  4. Motion Maps: Draw a motion map for an object that is slowing down while moving to the right. Include velocity and acceleration vectors.
  5. Graphs: Sketch position-time, velocity-time, and acceleration-time graphs for a ball rolling up a ramp, stopping, then rolling back down.
  6. Energy: A 2 kg object is lifted 5 meters. How much gravitational energy is stored? (Use g = 10 m/s²)
  7. Final Velocity: A car accelerates at 3 m/s² for 8 seconds. If it started at 5 m/s, what is its final velocity?

Unit 4: Balanced Forces, Motion, and Energy Transfer

Key Concepts

  • Force: A push or pull – an interaction between objects
  • Forces always come in agent-object pairs (e.g., FHS = force of hand on spring)
  • Balanced forces (ΣF = 0): Object at rest or moving at constant velocity
  • Forces are vectors – they have magnitude AND direction
  • Common forces:
    • Gravitational (Fg or weight)
    • Normal (N or ⊥) – perpendicular to surface
    • Tension (T) – pull from rope/string
    • Friction (f) – opposes motion
    • Applied (P) – push or pull
  • Fields: Allow objects to interact at a distance (gravitational and electric)

Force Diagrams

  • Represent object as a dot (point particle)
  • Draw force vectors originating from the dot
  • Label each force with agent-object notation (e.g., FEO = Earth on object)
  • Length of arrow = relative magnitude of force
  • Direction of arrow = force direction
  • Net force = vector sum of all forces

Key Equations

Gravitational force (weight): Fg = mg
(near Earth’s surface)

Gravitational field strength: g = 9.8 N/kg or 10 N/kg

Hooke’s Law: Fspring = kΔx
(k = spring constant)

Elastic energy: ΔEel = ½k(Δx)²

Work: W = F·Δx
(force across distance)

Coulomb’s Law: FE = kq₁q₂/d²

Universal Gravitation: Fg = Gm₁m₂/d²

What You Should Be Able To Do

  • Draw accurate force diagrams with proper labels
  • Identify balanced vs. unbalanced force situations
  • Calculate gravitational force (weight) from mass
  • Use Hooke’s Law to solve spring problems
  • Calculate work done by forces
  • Relate force diagrams to energy bar charts
  • Solve equilibrium problems (forces balanced)
  • Apply field concepts to gravitational and electric forces

Unit 4 Practice Questions

  1. Force Diagrams: Draw a force diagram for a book resting on a table. Label all forces using agent-object notation.
  2. Weight: What is the weight of a 5 kg object? (Use g = 10 N/kg)
  3. Balanced Forces: A box hangs from two strings. The tension in the top string is 50N and the tension in the bottom string is 20N. What is the weight of the box?
  4. Hooke’s Law: A spring with spring constant k = 100 N/m is stretched 0.2 m. What force does it exert?
  5. Work: You push a box with 30N of force across 4 meters. How much work do you do?
  6. Equilibrium: A person pushes a 40 kg box with 150N of force, but the box doesn’t move. What is the friction force?
  7. Multiple Forces: A 3 kg object is pulled upward by a string with 40N of tension. Draw a force diagram and determine if the forces are balanced.

Unit 5: Unbalanced Forces, Motion, and Energy Transfer

Key Concepts – Newton’s Laws

  • Newton’s 1st Law: Objects at rest stay at rest; objects in motion stay in motion (at constant velocity) unless acted on by unbalanced forces
  • Newton’s 2nd Law: ΣF = ma (unbalanced force causes acceleration)
  • Unbalanced forces cause changes in velocity (acceleration)
  • More force → more acceleration (if mass constant)
  • More mass → less acceleration (if force constant)
  • Force and acceleration are vectors – direction matters!

Energy Connections

  • Kinetic energy: Ek = ½mv²
  • Gravitational energy: ΔEg = mgΔh
  • Work-Energy Theorem: Work done = change in kinetic energy
  • Work: W = F·Δx (constant force parallel to displacement)
  • Internal Energy (Eint): Energy dissipated by friction, stored as temperature increase and structural changes
  • When friction acts: Eint = Ffriction · Δx
  • System definition matters! Including surfaces captures internal energy

Key Equations

Newton’s 2nd Law: ΣF = ma or a = ΣF/m

Kinetic energy: Ek = ½mv²

Gravitational energy: ΔEg = mgΔh

Work: W = F·Δx (constant force)

Work-Energy: W = ΔEk

With friction: Ek,initial = Ek,final + Eint
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