The whistle on a train produces a sound wave with a particular pitch. which of the following best describes the whistle sound that a person perceives while the train approaches him or her? a. a higher pitch, then a lower pitch b. the same pitch c. a higher pitch d. a lower pitch

When fat comes in contact with sodium hydroxide, it produces soap and glycerin. determine whether this is a physical change or a chemical change. explain your answer

Light from a sodium lamp passes through a diffraction grating that has 1000 slits per millimeter. the interference pattern is viewed on a screen 1.000 m behind the grating. the first (m = 1) two bright yellow fringes that are visible are 0.7288 m and 0.7300 m from the central maximum. what are the wavelengths of these two fringes?

If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?