音速

音 = 日 + 立 : Mnemonic symbol: a loudspeaker.

音 = 日 + 立 : Maud Younger and the Sun opened a pop-up store in front of the encampment. They sell vases and advertise them using loudspeakers, playing loud music and dancing to it.

速 = 束 + 辶 : Susan Saint Bernard tries out a new way of moving much faster in the space station's bathroom. She attached a bundle of firewood to each of her legs, and attached gladiator sandals to the ends of the bundles. This way she extends her legs and increases her speed dramatically.