Science1 course

Physics

Kinematics, forces, energy, momentum and circuits, with formula calculators that show every step.

About Physics

Physics explains how matter and energy behave, from a ball thrown across a field to current in a circuit. Introductory courses cover motion (kinematics), forces and Newton's laws, energy and momentum, waves, and electricity, and each topic is built on a small number of laws written as equations.

Problem solving in physics is a repeatable process: identify what is known, choose the law that connects it to the unknown, solve algebraically, and only then substitute numbers with units. Many problems that look different, such as a block on a slope and a car on a banked curve, use exactly the same idea, $\sum F = ma$ .

Physics underlies engineering, medicine, energy, electronics and transport. It is also the place where algebra, trigonometry and calculus are used most directly, so it strengthens those skills, and many science and engineering degrees require at least a year of it.

Introductory Physics

Algebra-based mechanics and simple circuits. (High school)

Kinematics

Kinematics describes motion without asking what causes it. Position, displacement, velocity and acceleration are the core quantities. Displacement and velocity are vectors, so direction matters: walking 5 m east and then 5 m west covers 10 m of distance but zero displacement.

Forces and Newton's Laws

A force is a push or pull, measured in newtons. Newton's first law says an object keeps its velocity unless a net force acts on it. The second law, $F_{\text{net}} = ma$ , says the net force sets the acceleration. The third law says forces come in equal and opposite pairs acting on different objects.

Work and Energy

Work is done when a force moves an object: $W = Fd\cos\theta$ , where $\theta$ is the angle between force and displacement. Energy is the capacity to do work. Kinetic energy $\frac{1}{2}mv^2$ belongs to moving objects; gravitational potential energy $mgh$ depends on height.

Momentum

Momentum is mass times velocity, $p = mv$ , a vector measured in kg·m/s. A heavy truck and a fast bullet can have similar momenta. A force applied over time changes momentum; this impulse $J = F\Delta t = \Delta p$ explains why airbags and crumple zones reduce injuries by stretching out the collision time.

Full Introductory Physics course outline

How to study Physics

Draw a free-body diagram for every force problem, with each force labelled and pointing the right way.
Solve symbolically first and plug in numbers last; it reduces arithmetic errors and lets you check units.
Check units and the size of the answer: a car's speed of 3000 m/s means something went wrong.
Choose a sign convention (for example, up is positive) and keep it for the whole problem.

Before you start: Algebra and right-triangle trigonometry; calculus helps for university courses.
Where it leads: AP Physics, engineering mechanics or electricity and magnetism.

Key terms in Physics

Vector: A quantity with size and direction, such as velocity or force. Vectors add tip to tail or component by component.
Newton's second law: The net force on an object equals its mass times its acceleration, $\vec F_{\text{net}} = m\vec a$ .
Free-body diagram: A sketch of one object with every force on it drawn as an arrow; it is the first step in almost every dynamics problem.
Conservation of energy: In a closed system the total energy stays constant; kinetic energy $\tfrac12 mv^2$ and potential energy trade places.
Momentum: Mass times velocity, $\vec p = m\vec v$ . With no outside force, total momentum before a collision equals total momentum after.
Significant figures: The digits in a measurement that carry real information; a final answer should not claim more precision than the data.