For typical rubber-on-concrete friction, what is the shortest time in which a car could accelerate from 0 to 50 mph? suppose that μs=1.00 and μk=0.80. express your answer to two significant figures and include the appropriate units.

First, let's convert the speed from mph to m/s, keeping in mind that
1 mi = 1609 m
1 h = 3600 s
So

The car starts with initial speed and reaches in a certain time .
In order for the car to accelerate, we must have that the force pushing the car (mass x acceleration) is at least equal to the frictional force, pointing into the opposite direction. We can consider only the dynamic frictional force, since the static frictional force acts only in the very first moment of the motion:

where and .
The acceleration is also given by

since . Substituting in the first formula, we get

From which we can find the time necessary to reach the mentioned velocity:

Magma  is composed of molten rock and is  stored  in the earth's crust. lava is  magma  that reaches the surface of our planet through a volcano vent.