Motion & Mechanics
Learn motion, distance and displacement, speed and velocity, acceleration, and equations of motion. Explore force, Newton's laws, inertia, and momentum. Use the simulator below: set initial velocity and acceleration, then Launch and Play / Pause to watch distance and speed over time.
- Displacement — shortest distance between positions (m)
- Velocity — rate of change of displacement (m/s)
- Acceleration — rate of change of velocity (m/s²)
- Force — interaction causing motion or deformation (N)
- Momentum — mass × velocity (kg·m/s)
Motion · Speed–Time Simulator
Adjust velocity and acceleration to observe distance and speed.
Key formulas
Real-world applications
Vehicle braking
Stopping distance depends on initial speed and deceleration; v² = u² + 2as links them.
Key insight: Higher speed means much longer stopping distance for the same deceleration.
Sports motion
Projectiles and runners follow kinematics; acceleration can be constant or changing.
Key insight: Velocity–time and position–time graphs describe real motion.
Elevators
Elevator motion involves acceleration (start/stop) and constant velocity (cruise).
Key insight: You feel heavier when accelerating up, lighter when accelerating down.
Common misconceptions & tips
In the absence of air resistance, all objects fall with the same acceleration g. Mass does not affect the rate of fall.
📘 F = ma implies a = F/m; greater weight is cancelled by greater mass.
🔢 a = g (same for all)
🧪 In the simulator, acceleration is set independently of mass.
Newton's first law: an object stays at rest or uniform motion unless acted on by a net force. No force is needed to maintain constant velocity.
📘 Friction is what slows things down; in the absence of friction, motion continues.
🔢 F = 0 ⇒ constant v
🧪 Set acceleration to zero in the sim to see constant velocity.
Deceleration is acceleration that opposes velocity (object slows down). In one dimension with positive velocity, deceleration has a negative sign.
📘 Deceleration is a matter of direction relative to velocity, not a separate quantity.
🔢 a opposite to v ⇒ speed decreases
🧪 In the sim, negative acceleration reduces speed.
Tip: In the simulator, set u and a then launch; check that the speed–time graph matches v = u + at.
Chapter Guide
How to Study This Chapter
- Start with Motion and reference frames
- Build concepts: Displacement → Velocity → Acceleration
- Connect ideas using equations of motion
- Apply force, Newton's laws, and momentum in the simulator
What You'll Learn
- Relate displacement, velocity, and acceleration
- Use kinematic equations for constant acceleration
- Apply Newton's laws and F = ma
- Interpret momentum and conservation
Subtopics – Motion & Mechanics
Each subtopic has a dedicated page with clear explanations and an interactive simulator where relevant.
Motion
Motion is the change in position of an object with time. It is described using quantities such as distance, displacement, speed, velocity, and acceleration.
Read more →Distance and Displacement
Distance is the total path length; displacement is the straight-line change in position from start to end. Distance is a scalar, displacement is a vector.
Read more →Speed and Velocity
Speed is the rate of change of distance (scalar); velocity is the rate of change of displacement (vector). Average and instantaneous values are used in kinematics.
Read more →Acceleration
Acceleration is the rate of change of velocity. It is a vector. Uniform acceleration means constant rate of change of velocity (e.g. free fall near Earth).
Read more →Uniform and Non-uniform Motion
Uniform motion: constant speed in a straight line. Non-uniform motion: changing speed and/or direction. These ideas lead to graphs and equations of motion.
Read more →Graphical Representation of Motion
Position–time, velocity–time, and acceleration–time graphs help visualise motion. Slope and area under curves give velocity and displacement.
Read more →Equations of Motion
For uniformly accelerated motion in a straight line: v = u + at, s = ut + ½at², v² = u² + 2as. Here u = initial velocity, v = final velocity, a = acceleration, s = displacement, t = time.
Read more →Force
Force is a push or pull that can change the state of motion or shape of an object. It is a vector. SI unit is the newton (N).
Read more →Newton's Laws of Motion
First law: inertia. Second law: F = ma. Third law: action and reaction are equal and opposite. These laws form the foundation of classical mechanics.
Read more →Inertia
Inertia is the tendency of an object to resist changes in its state of rest or uniform motion. Mass is a measure of inertia.
Read more →Momentum and Conservation of Momentum
Momentum p = mv. In an isolated system, total momentum is conserved. This principle is used to analyse collisions and explosions.
Read more →