Potential Energy Calculator
Compute gravitational potential energy PE = m g h with mass (kg), g and height (m).
Ep = — J
Potential energy: gravitational and elastic
Potential energy (Ep) is energy a system holds because of where its parts sit or how they're arranged. You'll meet two forms most often. There's gravitational, Ep = m·g·h, and elastic, Ep = (1/2)·k·x², where k is the spring constant and x the deformation away from equilibrium. At Earth's surface g ≈ 9.81 m/s², though it drifts a bit (9.78 at the equator, 9.83 at the poles). Lift a 2 kg body to 5 m and it stores about 98 J. The conservation of mechanical energy says Ec + Ep stays constant when nothing dissipates, which is what makes the simple pendulum period T = 2π√(L/g) work, with Ec and Ep trading back and forth.
Applications
Hydroelectric plants turn gravitational Ep into electricity (Itaipu runs 14 GW installed). Roller coasters, objects in free fall, ballistics, and pumped-storage batteries all lean on the Ep ↔ Ec swap. Over in chemistry, bond energy is a kind of potential energy; in electricity, electric Ep works out to qV.
FAQ
Does the reference level matter? What carries physical meaning is the difference in Ep, not its absolute value. Pick whatever reference you like, the floor, a tabletop, sea level. The work done depends on Δh, not on the height measured from zero.
Is elastic Ep always positive? Yes. Because x² can never go below zero, the spring stores energy either way, whether you stretch it or squeeze it.
Why does a pendulum slow down? Real systems bleed energy into air drag and friction at the pivot. As the mechanical energy drops, the swing gets smaller and smaller until the pendulum stops.
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Energy per Elevator Trip
Calculate the potential energy spent to raise a load, E = m·g·h, from the unbalanced mass m (net load after the counterweight, kg), gravity g and the lift height h (m). The result, in joules, is the minimum theoretical energy to hoist the load — a basis for estimating the elevator's electrical consumption and the energy-regeneration potential. Modern elevators with regenerative drives recover part of this energy on descent (when the counterweight descends with a light car), feeding it back to the grid. Actual consumption is higher, divided by the efficiency. Enter the unbalanced mass and the lift height.
Extrusion Specific Energy (SEC)
Calculate the extrusion specific energy consumption (SEC), SEC = power ÷ mass throughput, from the screw motor power (kW) and the mass throughput (kg/h). The result, in kWh/kg, is the energy to process each kilogram of polymer, and the main ENERGY-EFFICIENCY indicator of an extruder. Since extrusion melts and pumps plastic largely by VISCOUS heating (screw mechanical energy converted to heat by shear), specific consumption directly reflects how well the screw is doing its job. Typical values are 0.1-0.4 kWh/kg, varying with polymer (each has a melting enthalpy), screw geometry, speed and temperature. An abnormally HIGH SEC signals problems — wrong screw, excessive shear (which can degrade the material), poor temperature setting — and energy waste (the largest part of an extruder's operating cost). A very low SEC may indicate incomplete melting. Monitoring SEC is central to efficiency, quality and cutting cost and emissions in plastics processing. Enter the power consumed and the mass throughput.
Braking Energy
Calculate the energy dissipated in braking, E = ½·m·(v₁² − v₂²), from the mass m (kg), the initial velocity v₁ and the final velocity v₂ (m/s). When a vehicle or machine brakes, its KINETIC energy is converted — by brake friction — into HEAT. The dissipated energy is the kinetic-energy change: braking to a stop (v₂ = 0) dissipates all the initial kinetic energy; partial braking, the difference. This heat must be ABSORBED and DISSIPATED by the brake without overheating beyond the limit (above which the friction material loses effectiveness — fading — and may even burn or glaze). That is why brakes for heavy vehicles, long descents (mountain trucks) and severe duty need large thermal capacity (big, vented discs, or auxiliary brakes like engine braking and retarders, dissipating energy by other means without overloading the service brakes). Braking energy grows with the SQUARE of velocity: braking from 100 km/h dissipates FOUR times more energy than from 50 km/h — so high-speed braking is so much more demanding. This is the basis of brake thermal design and overheating checks in repeated or prolonged braking. Enter the mass and the initial and final velocities.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.