Answer:
v = 5 m/s
Explanation:
Given that,
The distance covered by a runner, d = 400 m
Time, t = 80 sec
We need to find the runner's average speed. It is equal to total distance covered divided by time taken. It can be given by:

So, the runner’s average speed is 5 m/s.
Answer:
The theory of Continental Drift suggest that hundreds of years ago all the continents were one big continent called Pangea. Soon these contintents split up created the places that we live today. This theory was introduced by Alfred Wegener. His colleges thought he was crazy, but later studies proved his impossible theory to be true. By the process of "sea floor spreading" the continents were then ripped apart and drifted to where they are today.
Answer:
minutes
Explanation:
For a First order reaction, the rate constant is determined by

Where
k= rate constant
t= time required for a reaction
a= initial concentration
x= amount of reactant decomposed in time t
a-x= amount of reactant left after time t
Let the initial concentration be 
Then

Substituting the given values in above equation, we get -


Also,

minutes
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Answer:
Because of cell differentiation
Explanation:
Multicellular organisms are organisms that have many cells in their body system, unlike unicellular organisms that have just one. However, these many cells contained in a multicellular organism are of different types performing different functions.
Although they all have the same set of genes encoding the same proteins in them, they are able to become different and perform different functions via a process called CELL DIFFERENTIATION. Cell differentiation is the process whereby cells of a living organism becomes specific in their functions as they divide. This is a result of the REGULATED EXPRESSION OF GENES. The genes in each cell are not expressed at the same time, hence, they have different functions.