Physics Calculators

About these calculators

This category holds three calculators for core physics and electronics relationships. Speed, Distance & Time Calculator solves for whichever of the three you leave out, with distance in kilometers, time in hours and speed in kilometers per hour, and it refuses a time or speed of zero when it would have to divide by it. Ohm's Law Calculator solves for voltage, current or resistance in a simple DC circuit and always shows the power as well, using volts, amps and ohms. Kinetic Energy Calculator finds the energy of a moving object from its mass in kilograms and its velocity in meters per second, giving joules and kilojoules.

Kinetic energy grows with the square of velocity, so doubling the speed quadruples the energy for the same mass. Each tool shows its formula and a worked example on its own page. They deal with single values, so there is no motion over changing speeds, no AC circuit analysis with impedance and no friction or air resistance. Units are fixed in the input boxes, which means a speed in miles per hour or a mass in pounds has to be converted first. The Unit Conversion category covers conversions such as acceleration, energy, power and pressure, and the results update as you type. The calculations run in your browser.

A few results to compare with your own. Driving 150 km in 2.5 hours is a speed of 60.00 km/h, and covering 300 km at 80 km/h takes 3.75 hours. Across 12 volts, a 4 ohm resistor passes 3.000 amps and uses 36.000 watts. A 1,200 kg car moving at 20 m/s carries 240,000 joules (240.000 kJ) of kinetic energy, and at 40 m/s that becomes 960,000 joules, exactly four times as much. Asking the Ohm's Law tool for a resistance with a current of zero returns the message that current cannot be zero, since the division is impossible. These are idealized textbook relationships, so a real motor, battery or braking distance will differ.