Understanding the laws of nature
Use the equations of motion for constant acceleration to find an object's final velocity v and displacement s from its initial velocity u, the elapsed time t, and the acceleration a. The relationships are v = u + a*t and s = u*t + 0.5*a*t^2. Enter any real values below and press calculate.
Our curriculum spans the major branches of physics. Each topic below has its own set of lessons, worked problems, and laboratory activities built around real measurements.
Three opening lessons that set the tone for how we study physics: start from a measurable situation, build a mathematical model, and then test it against real data.
Describing motion
Kinematics is the study of motion without regard to its causes. Position, velocity, and acceleration are the quantities we measure and relate. For motion with constant acceleration a, starting at initial velocity u, the velocity after time t is v = u + a*t, and the displacement is s = u*t + 0.5*a*t^2. These two equations let us predict how a falling or accelerating object will move.
The cause of acceleration
Mass resists a change in motion, and a net force causes a change. Newton's second law states that the net force on an object equals its mass times its acceleration, F = m*a. The same net force produces a smaller acceleration on a larger mass. This single rule explains everything from pushing a trolley to the trajectory of a rocket.
Voltage, current, and resistance
In a conductor, the current I that flows is proportional to the potential difference V across it, as long as the temperature stays constant. Ohm's law states V = I*R, where R is the resistance. A higher resistance means less current for the same voltage. This relationship is the starting point for analyzing almost every electric circuit.
A short practice question to check your grasp of forces. Choose an answer and we will mark it for you.
A 4 kilogram cart is pulled with a net force of 12 newtons. What is its acceleration?
Convert between common pairs of units used throughout physics and everyday life. Enter a value, choose the source and target units, and the conversion updates as you type.
The fundamental constants of physics, with standard SI values. Each card has a button that copies the value to the clipboard.
2.998e8 m/s
Speed of light c in vacuum. Exact value set by definition as 299 792 458 m/s.
6.674e-11
Gravitational constant G in N*m^2/kg^2.
6.626e-34
Planck constant h in J*s.
9.109e-31
Electron mass m_e in kg.
6.022e23
Avogadro number N_A, particles per mole.
1.602e-19
Elementary charge e in coulombs.
No. Every experiment on this site can be followed with a stopwatch, a ruler or tape measure, and simple household objects such as a pendulum made from a string and a small weight. Where specialist apparatus appears in a lesson, we describe exactly how a school laboratory would run it, and we always show the data and uncertainty so you can check the units and the physics without owning the instrument.
You need comfortable algebra: solving for one unknown, rearranging equations, and working with powers and square roots (for example T = 2*pi*sqrt(L/g)). Trigonometry with sine and cosine is helpful for vectors, forces, and projectile motion. We introduce and explain every formula in place with its symbols and units, so a solid algebra background is enough to start.
The simulations on this site solve the actual governing equations with real SI values. For example, the pendulum uses T = 2*pi*sqrt(L/g) with g = 9.81 m/s^2, and the projectile tool integrates with a real value of g. This means the numbers you see match what a physical apparatus would produce, and they reproduce published textbook results.
Yes, for the low-risk activities described, which use stationary or slow-moving masses and ordinary items. Keep any swinging pendulum away from fragile objects and eyes, use card rather than glass where possible, and never combine mains electricity with water. Full safety guidance appears on the laboratory page, and a responsible adult should supervise younger learners.
The curriculum is aligned with the common topic lists of A Level physics and the IB Diploma Programme, covering mechanics, thermal physics, waves, electricity and magnetism, circular and rotational motion, and modern physics, including the photoelectric effect and special relativity. Our worked examples and error-analysis practice are chosen to support those syllabi, though we are not an approved exam board course.
Yes. All lessons, the laboratory write-ups, the calculators, and every diagram are available free of charge. There are no paywalls and no ads. Any optional materials, should they ever be introduced, will always clearly state their price before you choose them.