A smoke detector is an electronic fire-protection device that automatically senses the presence of smoke as a key indicator of fire and creates a loud sound as a warning. In 3-5 sentences, describe what is happening inside a photoelectric smoke detector as soon as smoke enters it

Which of the statements about waves is true? a. in longitudinal waves, particles move perpendicular to the direction the wave is traveling.b. both transverse and longitudinal waves can travel through water c. electromagnetic waves are a type of longitudinal waves.d. in a transverse wave, particles move parallel to the direction the wave is traveling.

Henry, whose mass is 95 kg, stands on a bathroom scale in an elevator. the scale reads 830 n for the first 2.4 s after the elevator starts moving, then 930 n for the next 2.4 s. part a what is the elevator's speed 4.8 s after starting? express your answer with the appropriate units.

In science and physics what is the standard unit of measure for speed?