The equation for the Doppler shift of a sound wave of speed v reaching a moving detector is

fd = fs [(v + vd) / (v-vs)]

where vd is the speed of the detector, vs is the speed of the source, fs is the frequency of the source, fd is the frequency of the detector. If the detector moves toward the source, vd is positive; if the source moves toward the detector, vs is positive.

A train moving toward a detector at 31 m/s blows a 305-Hz horn. What frequency is detected by
a. a stationary train?
b. a train moving toward the first train at 21 m/s?

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

yo yo yo its papaguy in the house lol

okay, ima .

um it shows links to uh so kinda microsoft website is that were ima go or no? ?

the answer is ampere

the ampere is used to measure electricity. an ampere is a unit of electric current equal. a unit of measure for the flow of current in a circuit. one ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance.