action
activity
balance
bright
brown
bulb
colliding
concept
conservation
conserve
cradle
economical
effect
efficiency
electric
energy
force
fuel
glass
glowing
gravity
hanging
illuminated
illumination
impact
incandescent
innovation
invention
lamp
light
mass
motion
old fashioned
oscillation
pendulum
perpetual
physics
plank
power
recycle
retro
save
science
shine
solution
swinging
technology
vintage
wire
wood