Edexcel GCSE Physics: Motion and Forces

Vectors & Scalars

• Vector: Magnitude and direction
• Scalar: Magnitude only
• Vectors can be negative depending on direction; scalars generally cannot.

Examples

• Scalar: Speed, Distance, Time, Mass, Energy
• Vector: Velocity, Displacement, Acceleration, Force, Momentum

Key Concept

• Displacement can be positive or negative based on reference point.
• Speed becomes velocity when direction is specified.

Graph Analysis

Displacement-Time Graphs

• Gradient: Velocity
  • Sharper gradient = faster speed
  • Negative gradient = returning to start
• Horizontal line: Stationary
• Area under line: Not applicable
• Curved line indicates changing velocity (acceleration)

Velocity-Time Graphs

• Gradient: Acceleration
  • Sharper gradient = greater acceleration
  • Negative gradient = deceleration
• Horizontal line: Constant speed
• Area under line: Distance travelled
• Curved line indicates changing acceleration

Speed Calculations

Average Speed

• Use overall distance and timing:
  • Average Speed = Total Distance / Total Time

Methods to Determine Speed

• Constant Speeds: Measure distance & time
• Light Gates: More accurate, eliminates human error

Typical Speeds

• Wind: 5-7 m/s
• Sound: 340 m/s
• Walking: ~1.4 m/s (5 km/h)
• Running: ~3 m/s
• Cycling: ~4 m/s
• Bus: 14 km/h
• Train: 125 mph
• Plane: 900 km/h

Acceleration and Newton's Laws

Acceleration due to Gravity

• Standard: 10 m/s^2

Newton’s First Law

• Objects maintain constant velocity unless acted on by a resultant force.

Newton’s Second Law

• Formula: F = ma
• Force, mass, and acceleration relationship

Newton’s Third Law

• Every action force has an equal and opposite reaction force.

Circular Motion

• Constant speed but changing direction implies acceleration.
  • Centripetal Force: Directed towards center

Momentum

• Conserved in collisions without external forces
• Formula: p = mv
• Newton’s Second Law: F = Δp / t

Human Reaction and Stopping Distances

Human Reaction Time

• Average: 0.25 seconds
• Measured via Ruler Drop Experiment

Vehicle Stopping Distance

• Influenced by: Reaction Time, Speed, Road Conditions, Vehicle Mass
• Thinking Distance: Distance during reaction time
• Braking Distance: Distance from braking to stop

Dangers of Large Decelerations

• High forces during crashes due to rapid deceleration

Work Done to Stop

• Equal to initial kinetic energy
• Relates to braking distance

Mathematical Skills

• Unit conversion, graph interpretation
• Calculations for distance, speed, time, force, and acceleration
• Estimations for stopping distances and forces in transport scenarios.