Why does a siren have a higher pitch as it approaches you?

The amplitude of the sound wave is increased.

The crests of the sound wave are spaced closer together.

The troughs of the sound wave are farther apart.

The period of the sound wave is increased.

Find v(t), given acceleration a(t)=7j and initial velocity v(0)=k

If you place a magnet under a clear dish, and sprinkle iron fillings over it, above what part of the magnet will most of the fillings gather

Acarpenter builds an exterior house wall with a layer of wood 2.9 cm thick on the outside and a layer of styrofoam insulation 2.3 cm thick on the inside wall surface. the wood has k=0.080w/(m⋅k), and the styrofoam has k= 0.010 w/(m⋅k). the interior surface temperature is 19.0 ∘c , and the exterior surface temperature is -15.0 ∘c . a.)what is the temperature at the plane where the wood meets the styrofoam? celsius b.)what is the rate of heat flow per square meter through this wall? /m^2