Answer:
During the section CD , the speed is fastest.
Explanation:
The rate of change of distance is called speed.
Speed = distance / time
Its SI unit ism/s. It is a scalar quantity.
The slope of the distance time graph is given by the speed of the object.
Here, the speed of AB is 30/3= 10 m/s .
The speed of BC is = 0 m/s
The speed of CD is (50 - 30)/(6 - 5) = 20 m/s
So, the speed is maximum during the section CD.
the answer of this question is helium
Answer:
Explanation:
Given
length of window 
time Frame for which rock can be seen is 
Suppose h is height above which rock is dropped
Time taken to cover 
so using equation of motion

where y=displacement
u=initial velocity
a=acceleration
t=time
time taken to travel h is

Subtract 1 and 2 we get


and from equation 
so 

and 
so 



substitute the value of
in equation 2


I am sure it is frequency
Air pollution!! Can I have brainlyist:))