What is the average speed of the swimmer between the times t=0 st=0\text{ s} t=0 s t, equals, 0, start text, space, s, end text and t=8 st=8\text{ s} t=8 s t, equals, 8, start text, space, s, end text ?

1 unit of lenght per second (it may be meters, but there is no enough information)

Explanation:

If t is time and s is position, we have that:

in t= 0s, s(t) = 0

in t= 8s, s(t) = 8

Then, we can see that the swimmer moved 8 units in the lapse of 8 seconds, and the average speed can be calculated as:

s = distance/time = 8units/8s = 1 unit per second.

So the average speed of the swimmer in that lapse of time is one unit per second, where unit depend on the problem, here may be metters.

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.