# Space, time and motion

> IB Physics SL · IB Physics SL 2025
> Source: https://www.owlsprep.com/study/ib-physics-sl-u1-overview/
> Weight: 20-22% of overall IB Physics SL exam

This foundational core unit introduces core mechanics concepts that underpin all of physics, from everyday motion to orbital dynamics. You will build quantitative skills to describe, predict, and analyze motion across common physical scenarios.

**Prerequisites:** High school algebra and basic trigonometry; Familiarity with SI units for fundamental quantities

## Learning objectives

- Describe motion using fundamental kinematic quantities and equations for constant acceleration
- Analyze forces, momentum, and energy interactions to solve 1D and 2D mechanics problems
- Apply Newton's laws and gravitation to model circular and orbital motion
- Connect core mechanical concepts to real-world everyday and astrophysical motion scenarios

## Unit at a glance

This unit follows a logical learning arc: you will start by describing motion without considering its causes (kinematics), then move to what causes changes in motion (forces and momentum), next explore energy transfers that accompany motion, and finally apply all previous concepts to curved and orbital motion.

Concepts from this unit are tested across both Paper 1 (MCQ) and Paper 2 (structured response) of the IB Physics SL exam, and are required for all subsequent units in the syllabus.

The unit is split into 4 core sub-topics:
- [Kinematics](https://www.owlsprep.com/study/ib-physics-sl-u1-kinematics/) — Describes motion in 1 and 2 dimensions using displacement, velocity, acceleration and kinematic equations.
- [Forces and momentum](https://www.owlsprep.com/study/ib-physics-sl-u1-forces-and-momentum/) — Covers Newton's laws of motion, free-body diagrams, impulse, and conservation of momentum for collisions.
- [Work, energy and power](https://www.owlsprep.com/study/ib-physics-sl-u1-work-energy-and-power/) — Introduces work done, energy conservation, kinetic/potential energy, and power calculations.
- [Circular motion and gravitation](https://www.owlsprep.com/study/ib-physics-sl-u1-circular-motion-and-gravitation/) — Applies previous concepts to uniform circular motion, Newton's law of gravitation, and orbital motion.

## Common pitfalls

- **Wrong:** Mixing up scalar and vector quantities when adding or resolving motion components
  - Why it fails: Vectors require direction when combining, while scalars only add numerically regardless of direction
  - Correct: Always resolve vectors into perpendicular x/y components before combining or calculating results
- **Wrong:** Treating centripetal force as an extra separate force acting on a rotating object
  - Why it fails: Centripetal force is the net resultant force towards the center of rotation, not an additional force
  - Correct: Draw all individual acting forces first, then calculate the net force that acts as centripetal force
- **Wrong:** Applying conservation of momentum/energy without checking for external forces
  - Why it fails: External forces change total momentum and do work that changes total mechanical energy
  - Correct: Confirm the system is closed (no net external force) before applying conservation laws

## Cheatsheet

| Concept | Key Formula/Rule |
| --- | --- |
| SUVAT (constant acceleration) | $v = u + at$, $s = ut + \frac{1}{2}at^2$, $v^2 = u^2 + 2as$ |
| Newton's Second Law | $F_{net} = ma = \frac{\Delta p}{\Delta t}$ |
| Conservation of Momentum | $\sum p_{initial} = \sum p_{final}$ |
| Work done | $W = Fs\cos\theta = \Delta E_k$ |
| Conservation of Mechanical Energy | $\Delta E_k + \Delta E_p = 0$ (no resistive forces) |
| Centripetal acceleration | $a_c = \frac{v^2}{r} = \omega^2 r$ |
| Newton's Law of Gravitation | $F = G\frac{M_1 M_2}{r^2}$ |
| Orbital speed | $v = \sqrt{\frac{GM}{r}}$ |

## What's next

Begin your study of this foundational unit with the first sub-topic on Kinematics, where you will master the core definitions and equations needed to describe motion in 1D and 2D. This knowledge will underpin every subsequent sub-topic in this unit. Once you complete all four sub-topics here, you can move on to the next core IB Physics SL unit on Thermal Physics.

- [Kinematics (First sub-topic of this unit)](https://www.owlsprep.com/study/ib-physics-sl-u1-kinematics/)
- [Thermal Physics (Next unit)](https://www.owlsprep.com/study/ib-physics-sl-u2-overview/)
- [Forces and momentum](https://www.owlsprep.com/study/ib-physics-sl-u1-forces-and-momentum/)

---

From [OwlsPrep](https://www.owlsprep.com) — free study guides for A-Level, IB, AP and IGCSE, written against the official syllabus. Canonical page: https://www.owlsprep.com/study/ib-physics-sl-u1-overview/