Answer:
Ff = 159 [N]
Explanation:
Since in the problem give us two values of friction coefficient one static and the other dynamic, it is important to keep in mind that in order to solve this problem we must know the conditions in which the sled is located. We can read that the sled is in motion, in this way we use the dynamic coefficient of friction.
The friction force is calculated as the product of normal force, by the appropriate coefficient of friction value.
Ff = N * μ
Ff = 636 * 0.25
Ff = 159 [N]
Answer:


is the photon energy of an x-ray
Explanation:
Given:
Energy of photon, 
Then according to given:


is the wavelength
Again,
Energy of photon, 
wavelength of the light, 


<u>Now, photon energy for an x-ray:</u>
wavelength, 

is the photon energy of an x-ray
Answer:
See answer below
Explanation:
Hi there,
I'm a bit late with this response, but I attached the work below.
Good luck with physics, have fun!
thanks,
Number 20 is B and 21 is C
Answer:
0.235 nC
Explanation:
Given:
= the magnitude of electric field = 
= the magnitude of electric force on each antenna = 
= The magnitude of charge on each antenna
Since the electric field is the electric force applied on a charged body of unit charge.

Hence, the value of q is 0.235 nC.