you travel in a circle, whose circumference is 8 kilometers, at an average of 8 kilometers/hour. if you stop at the same point y
1 answer:
The average velocity is zero
Explanation:
The average velocity of an object is given by:
where
d is the displacement of the object
t is the time interval
The displacement is the distance in a straight line between the initial position and final position of motion.
In this problem, the person is travelling in a circle, and he stops at the same point where he started: this means that the initial position corresponds to the final position, therefore
displacement = 0
And so, the average velocity is also zero:
v = 0
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Answer:
The wavelength is 173 nm.
Explanation:
This kind of phenomenon is known as photoelectric effect, it occurs when photons of light inside the metal surface and if they have the right amount of energy electrons absorb it and got expelled from the metal as photo electrons. The maximum kinetic energy of that photo electrons is given by the expression:
(1)
With E the energy of the photon and Φ the work function of the material. The work function is a value characteristic of each material and is related with how much the electron is attached to the material, the energy of the photon is the Planck's constant (h=) times the frequency of light (
) , then (1) is:
(2)
The frequency of an electromagnetic wave is related with the wavelength () by:
(3)
with c the velocity of light (c=)
Using (3) on (2):
Solving for :
That's the work function of the metal we're dealing. So now if we want to know the wavelength to obtain the double of the kinetic energy we use:
Solving for :