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Conservation of Energy

Virtual Lab 2

Simple Pendulum

The bob exchanges potential and kinetic energy on every swing. Without friction the total mechanical energy is constant; with friction it drains away as heat.

Controls

1.5 m
1 kg
35 °
Period ≈ 2.52 s

Time

0.00 s

Angle

0.0°

Speed

0.00 m/s

Rise above B

0.00 m

At B the bob is fastest: kinetic energy is maximum and potential energy is minimum.

Live energy

PEPotential Energy0.00 J
KEKinetic Energy0.00 J
ETotal Energy0.00 J
AMaximum PE · Zero KE
BMaximum KE · Minimum PE
CMaximum PE · Zero KE
U=mgL(1−cos⁡θ)=0.00 JU = mgL(1-\cos\theta) = 0.00\ \mathrm{J}
K=12mv2=0.00 JK = \tfrac12 m v^2 = 0.00\ \mathrm{J}

Graphs

Friction: with and without

Friction OFF

No energy leaves the system. The bob returns to exactly the same height on every swing and K + U stays at 2.66 J.

Friction ON

Air resistance and friction at the pivot do negative work. Mechanical energy decreases and appears as heat — currently 0.00 J lost. Total energy of the universe is still conserved.