Answer:
Kinetic energy: 
Velocity: 
Explanation:
From the equations of the photo-electric effect,
We know:
Where,
1.
is the Planck's constant which is 
2.
are the frequency of light emitted and threshold frequencies respectively.
3.
is the kinetic energy of the electrons emitted.
By fact, we come to know that the threshold frequency of Zn is 300nm
And also 
Where ,
1. 
is the speed of light 
2.
is the wavelength.
Thus,
Now to find velocity:
Frequency = velocity of propagation / wavelength.
<span>For light, we assume it is moving in a vacuum, so vp is 3e8 m/s. The wavelength of 310nm is 310e-9 meters. Then we plug the numbers in, and we get (3e8 m/s) / (310e-9 m) = 967.742e12 Hz because 1/s is the same as cycles/sec, which is a Hertz.</span>
On eof the forces is inertia. This can happen when you move your furniture to clean under them. When you move an object in a straight line without chanign its composition (e.g moving a chair or a table from one side to the other) you are working with inertia. The secon force is friction. It s present when you clean a surface by rubbing it with a tool like a damp cloth or a mop.
