Answer:
The value is 
Explanation:
From the question we are told that
The rate at which the plate rotates is 
Generally the revolution per second is mathematically represented as

=> 
A:True because Lithium is the lighest solid and metal and the third lightest element.
The volume of rain that fells in the field is simply given by the area of the field, which is

multiplied by the height of rain that fell, which is

Therefore, the volume is

Answer:
b) 472HZ, 408HZ
Explanation:
To find the frequencies perceived when the bus approaches and the train departs, you use the Doppler's effect formula for both cases:

fo: frequency of the source = 440Hz
vs: speed of sound = 343m/s
vo: speed of the observer = 0m/s (at rest)
v: sped of the train
f: frequency perceived when the train leaves us.
f': frequency when the train is getTing closer.
Thus, by doing f and f' the subjects of the formulas and replacing the values of v, vo, vs and fo you obtain:

hence, the frequencies for before and after tha train has past are
b) 472HZ, 408HZ