Plzzz help!! A stationary speed gun emits a microwave beam at 2.10x1010 Hz. It
reflects off a car and returns 1030 Hz
higher. What is the speed of the car?
(Unit = m/s)

The speed of the car is 14.7m/second or 15 m/second approximately.

Explanation:

A microwave beam at is generated by a stationary speed gun. It bounces off a car and returns at a higher frequency of 1030 Hz. The car's observed frequency would be the product of adding the two frequencies. That is to say,

       F = =

Using doppler effect formula

Where

F = observed frequency

f = source frequency

C = speed of light =

V = speed of the car

 Putting the values in the formula -

by cross multiplication ,

   300000014.7 - 1.000000049V =

    Collect the like terms  

1.000000049V = 14.71429

      Make V the subject of formula

V =

V = 14.7 m/s

Therefore , the speed of the car is 15m/second approximately.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.