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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Answer:
don't know what class are you you are using which mobile or laptop
Answer:
Explanation:
The energy of a photon is given by the equation 
, where h is the <em>Planck constant</em> and f the frequency of the photon. Thus, N photons of frequency f will give an energy of 
.
We also know that frequency and wavelength are related by 
, so we have 
, where c is the <em>speed of light</em>.
We will want the number of photons, so we can write
We need to know then how much energy do we have to calculate N. The equation of power is 
, so for the power we have and considering 1 second we can calculate the total energy, and then only consider the 4% of it which will produce light, or better said, the N photons, which means it will be 
.
Putting this paragraph in equations:
.
And then we can substitute everything in our equation for number of photons, in S.I. and getting the values of constants from tables:
