Four calculators, one panel.
Pick a mode below — everything recalculates live as you type, and every result explains itself with the formula it came from.
Pick the unknown — the calculator asks for exactly the three values its formula needs.
Speed at the start — 0 for anything released from rest.
Speed at the end of the interval — negative if it reversed direction.
Change in speed per second — negative for braking. Free fall ≈ 9.81 m/s².
Duration of the motion — must be greater than zero.
The amount of matter — identical everywhere in the universe.
How quickly speed changes — negative when slowing down.
Gravity presets — or pick custom and enter your own g below.
Local gravitational acceleration in m/s² — 9.807 on Earth.
The amount of matter, in kilograms.
Speed — the sign doesn’t matter here, because v gets squared.
Height above your chosen zero level — negative means below it.
9.807 on Earth · 1.62 on the Moon · 3.721 on Mars.
The push or pull, assumed constant over the whole distance.
How far the object moves while the force acts.
0° pushes along the motion · 90° is sideways (zero work) · 180° pulls against it.
Two knowns are always enough — pick the one you’re missing.
Electrical push — 1.5 V for a AA battery, 120 V (US) or 230 V (EU) sockets.
Rate of flow — a fast-charging phone draws about 2 A.
How strongly the component opposes the current, in ohms.
From homework problem to answer in four steps.
No manual, no setup — this is the whole workflow.
Pick the topic
Choose the tab that matches your problem — motion, force & weight, energy & work, or electricity.
Point at the unknown
Every mode asks what you want to solve for — a dropdown or a switch — then shows exactly the inputs it needs.
Type what you know
Results recalculate live as you type. One-click example chips fill in classic problems so you can watch the tool think.
Read it, then re-derive it
The answer lands with its unit and plain-English meaning, plus the formula with your numbers substituted — ready to copy into homework.
Every formula it uses, on one card.
The same equations the calculator substitutes your numbers into — worth having in memory for exam day.
Equations of motion
s = ut + ½at²
v² = u² + 2as
s = ½(u + v)t
The SUVAT set. Each line uses a different three of s, u, v, a, t — so any three known values unlock the other two.
Newton's second law
Force (N) = mass (kg) × acceleration (m/s²). One newton is the push that speeds 1 kg up by 1 m/s each second.
Weight
Weight is a force, not a mass. The same 70 kg person: 686 N on Earth, 113 N on the Moon — the kg never change, the gravity does.
Mechanical energy
PE = mgh
Kinetic is energy of motion (v is squared — double the speed, quadruple the energy); potential is energy of position, banked by height against gravity.
Work
Energy transferred by a force over a distance. Push along the motion (0°) for full effect; sideways (90°) transfers nothing.
Ohm's law & power
P = V × I
Voltage equals current times resistance; power equals voltage times current. Two measurements pin down a whole circuit.
Physics questions, answered.
The eight things students ask most about motion, force, energy and Ohm's law — collected in one place.
How do I calculate final velocity?+
Use v = u + at — starting velocity u, plus acceleration a times time t. An object dropped from rest (u = 0) falling for 3 s at g = 9.81 m/s² reaches v = 0 + 9.81 × 3 = 29.43 m/s. The Motion tab solves this instantly and shows the distance covered too.
What are the SUVAT equations of motion?+
Four equations link the five quantities of constant-acceleration motion: v = u + at, s = ut + ½at², v² = u² + 2as and s = ½(u + v)t. Because each equation uses a different three of the five, knowing any three values is always enough to find the rest. Pick the quantity you want in the Motion tab and the calculator asks for exactly the three it needs.
How do I calculate force with Newton's second law?+
Multiply mass by acceleration: F = ma, with mass in kilograms and acceleration in metres per second squared, giving force in newtons. A 60 kg mass accelerating at 2 m/s² needs F = 60 × 2 = 120 N. One newton is defined exactly this way — the force that accelerates 1 kg at 1 m/s².
How do I calculate weight on the Moon or Mars?+
Weight is mass times local gravity: W = mg. Your mass never changes, but gravity does — 9.807 m/s² on Earth, 1.62 on the Moon and 3.721 on Mars. A 70 kg person weighs about 686 N on Earth, 113 N on the Moon and 260 N on Mars. The Force & weight tab has all these presets built in.
How do I calculate kinetic and potential energy?+
Kinetic energy is KE = ½mv² — a 1000 kg car moving at 20 m/s carries ½ × 1000 × 20² = 200,000 J. Potential energy is PE = mgh — lifting 100 kg up 2 m on Earth stores 100 × 9.807 × 2 ≈ 1961 J. Work done by a force is W = F × d × cos θ, also in joules, ready to compare with both.
How do I use Ohm's law to find voltage, current or power?+
Ohm's law says V = I × R: voltage in volts equals current in amps times resistance in ohms. Rearrange it for whatever is missing — I = V ÷ R or R = V ÷ I. Power follows from P = V × I, so a 120 V bulb drawing 0.5 A uses 60 W and has 240 Ω of resistance. The Ohm's law tab solves for any of the four.
What units does the physics calculator use?+
SI units throughout: metres (m), seconds (s), metres per second (m/s), newtons (N), kilograms (kg), joules (J), volts (V), amps (A), ohms (Ω) and watts (W). For convenience, energy results are also converted to food calories and kilowatt-hours, and weight to pounds-force.
Is this calculator free, and is my data sent anywhere?+
It is completely free and runs entirely in your browser — nothing you type is uploaded, logged, or sent to a server. No account, no sign-up, no limits.