Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: Figure 6.11 The frictional force supplies the centripetal force and is numerically equal to it. Centripetal force is perpendicular to velocity and causes uniform circular motion. The larger the F c , the smaller the radius of curvature r and the sharper the curve. The second curve has the same v , but a larger. Answer: centripetal force
[EX A]: What force is perpendicular to velocity and causes uniform circular motion?

[EX Q]: Passage: Sensory organs such as the eyes contain cells called sensory receptors that respond to particular sensory stimuli. Answer: sensory receptors
[EX A]: Sensory organs that respond to particular sensory stimuli contain cells called what?

[EX Q]: Passage: In radio broadcasts, sounds are encoded in radio waves by changing either the amplitude (AM) or frequency (FM) of the waves. The encoded waves are broadcast from a tower and changed back to sounds by radio receivers. Answer: radio receivers
[EX A]:
What changes encoded waves which are being broadcast into sounds?