If net external force acting on the system is zero, momentum is conserved. That means, initial and final momentum are same → total momentum of the system is zero.
A) We want to find the work function of the potassium. Apply this equation:
E = 1243/λ - Φ
E = energy of photoelectron, λ = incoming light wavelength, Φ = potassium work function
Given values:
E = 2.93eV, λ = 240nm
Plug in and solve for Φ:
2.93 = 1243/240 - Φ
Φ = 2.25eV
B) We want to find the threshold wavelength, i.e. find the wavelength such that the energy E of the photoelectrons is 0eV. Plug in E = 0eV and Φ = 2.25eV and solve for the threshold wavelength λ:
E = 1243/λ - Φ
0 = 1243/λ - Φ
0 = 1243/λ - 2.25
λ = 552nm
C) We want to find the frequency associated with the threshold wavelength. Apply this equation:
c = fλ
c = speed of light in a vacuum, f = frequency, λ = wavelength
Given values:
c = 3×10⁸m/s, λ = 5.52×10⁻⁷m
Plug in and solve for f:
3×10⁸ = f(5.52×10⁻⁷)
f = 5.43×10¹⁴Hz
Explanation:
Move the decimal point until it is behind the first non-zero digit.
In this case, we move it 3 places to the right so it is behind the 9.
Therefore, 0.0097 = 9.7×10⁻³.
Answer: As the "wind" pushes the blades and makes them to spin, kinda like an inverse process of how a fan works (where in the fan you impunt energy to make the blades move and generate wind, and in this case the wind makes the blades move to generate electricity), and this movement of the blades creates work that is transformed into electric energy.
Without the wind, you can not generate work in the blades, and then electric energy can not be generated, so you need this source to "push" and impulse torque in the blades.
<span>Just add the two kinetic energies;
E = (1/2)mv^2 + (1/2)mv^2</span>
