1) The average velocity is 
2) The instantaneous velocity is 
Explanation:
1)
The average velocity of an object is given by

where
d is the displacement
t is the time elapsed
In this problem, the position of the particle is given by the function

where t is the time.
The position of the particle at time t = 6 sec is

While the position at time t = 12 sec is

So, the displacement is

And therefore the average velocity is

2)
The instantaneous velocity of a particle is given by the derivative of the position vector.
The position vector is

By differentiating with respect to t, we find the velocity vector:

Therefore, the instantaaneous velocity at any time t can be found by substituting the value of t in this expression.
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The rate of change of velocity per unit time is called acceleration.
Its SI unit is m/s².

Answer:
Final speed of the car, v = 24.49 m/s
Explanation:
It is given that,
Initial velocity of the car, u = 0
Acceleration, 
Time taken, t = 7.9 s
We need to find the final velocity of the car. Let it is given by v. It can be calculated using first equation of motion as :

v = 24.49 m/s
So, the final speed of the car is 24.49 m/s. Hence, this is the required solution.
hi, so the material that would normally form mineral crystals does not have time to form a crystalline structure because of very rapid cooling after volcanically erupting into the air or onto the surface. Obsidian is a volcanic glass.