Physics Calculators — Mechanics, Optics & Thermodynamics

Speed is a scalar quantity — it tells you how fast something is moving. Velocity is a vector — it includes both speed and direction. An object moving in a circle at constant speed has changing velocity because its direction changes continuously.

Use the formula KE = ½ × m × v², where m is mass in kilograms and v is velocity in meters per second. The result is energy in Joules. Note that kinetic energy scales with the square of velocity, so doubling your speed quadruples your kinetic energy.

Our current tools focus on classical physics, which is accurate for everyday speeds (well below the speed of light). For objects moving at a significant fraction of light speed, relativistic corrections using the Lorentz factor would be needed. We plan to add relativistic calculators in a future update.

Gravitational force is calculated using Newton's Law of Universal Gravitation: F = G × (m₁ × m₂) / r², where G is the gravitational constant (6.67430 × 10⁻¹¹ m³ kg⁻¹ s⁻²), m₁ and m₂ are the masses of the two objects in kilograms, and r is the distance between their centers in meters. The force is always attractive. For example, the force between Earth and the Moon can be computed this way. Our gravitational force calculator lets you input masses and distance (in meters or kilometers) and instantly returns the force in Newtons.

Power is the rate at which work is done or energy is transferred, measured in watts (W), where 1 watt = 1 joule per second. The basic formula is P = W / t (power = work ÷ time) or P = F × v (force × velocity) when constant force is applied. For example, lifting a 100 N object 5 meters in 2 seconds: work = 500 J → power = 500 / 2 = 250 W. Our power calculator supports multiple formulas (work/time, force/velocity, energy/time) and unit conversions for quick physics or engineering calculations.

Momentum is the product of an object's mass and velocity: p = m × v, measured in kg·m/s. It is a vector quantity, so direction matters. For example, a 2 kg object moving at 5 m/s east has momentum of 10 kg·m/s east. Momentum is conserved in isolated systems (e.g., collisions). Our momentum calculator lets you input mass and velocity (with direction support) and computes linear momentum instantly, including impulse (change in momentum) for collisions.

Mass is the amount of matter in an object (measured in kilograms) and remains constant regardless of location. Weight is the gravitational force acting on that mass (measured in Newtons) and changes with gravity — weight = mass × gravitational acceleration (W = m × g). On Earth g ≈ 9.81 m/s², on the Moon g ≈ 1.62 m/s², so a 70 kg person weighs 686.7 N on Earth but only ~113 N on the Moon. Our mass to weight converter calculates weight on Earth, Moon, Mars, or any custom gravity value.