In the photoelectric effect, the energy of the incoming photon (E=hf) is used in part to extract the photoelectron from the metal (work function) and the rest is converted into kinetic energy of the photoelectron:

where
h is the Planck constant
f is the frequency of the incident light

 is the work function of the material
K is the kinetic energy of the photoelectron.
The photoelectron generally loses part of its kinetic energy inside the material; however, we are interested in its maximum kinetic energy, that is the one the electron has when it doesn't lose energy, so we can rewrite the previous equation as

The work function is (in Joule)

and using the data of the problem, we find the maximum kinetic energy of the photoelectrons
 
 
        
        
        
Answer: 5.41 V
Explanation:in order to explain this result we have to use the Ohm law given by:
ΔV=R*I where R is the resistance which is equal R= ρ*L/A . ρ is the resistivity, L the length of the wire and A is the cross section. I is the current.
Then we have
ΔV=ρ*L*I/A= 1.68 * 10^-8 Ωm*93.4 m*72.5A/2.1* 10^-5 m^2=5.41 V
 
        
             
        
        
        
They are important because numerous serve as areas where water vapour can condense.
<h3>
</h3><h3>What is condensation?</h3>
The transformation of water vapour into liquid is known as condensation. The process is the opposite of evaporation, in which liquid water turns into a vapour. Either the air is chilled to its dew point or it gets too saturated with water vapour to retain any more water, causing condensation to occur.
to learn more about condensation go to - 
brainly.com/question/1268537
#SPJ4
 
        
             
        
        
        
Answer:
(a) 

(b)
1120 N
Explanation:
Change in velocity,  is given by subtracting the initial velocity from the final velocity and expressed as
 is given by subtracting the initial velocity from the final velocity and expressed as 
Where v represent the velocity and subscripts f and i represent final and initial respectively. Since the ball finally comes to rest, its final velocity is zero. Substituting 0 for final velocity and the given figure of 8 m/s for initial velocity then the change in velocity is given by
 
To find  then we substitute 7 kg for m and -8 m/s for
 then we substitute 7 kg for m and -8 m/s for  therefore
 therefore 
(b)
The impact force, F is given as the product of mass and acceleration. Here, acceleration is given by dividing the change in velocity by time ie

Substituting t with 0.05 s then 
Since F=ma then substituting m with 7 Kg we get that F=7*-160=-1120 N
Therefore, the impact force is equivalent to 1120 N