Frequency: 
Explanation:
The force experienced by an electron in a magnetic field is

where
is the electron charge
v is the speed of the electron
B is the strength of the magnetic field
Since the force is perpendicular to the direction of motion of the electron, the force acts as centripetal force, so we can write:

where
r is the radius of the orbit
is the mass of the electron
Re-arranging the equation,
(1)
We also know that in a circular motion, the speed is equal to the ratio between circumference of the orbit and orbital period (T):

Substituting into (1),

We also know that 1/T is equal to the frequency f, so

In this problem,

Therefore, the frequency of the electrons is

Answer:
v2^2 - v1^2 = 2 g s fundamental formula
v2 = v1 + 2 g = v1 + 19.8 increase in velocity in 2 sec
v1^2 + 39.6 v1 + 392 - v1^2 = 2 * 9.8 * 123.1 = 2412.76
v1 = (2412.76 - 392) / 39.6 = 51.03
v2 = 51.03 + 19.6 = 70.63
T = 70.63 / .8 = 7.207 sec time to fall height of tower
S = 1/2 g T^2 = 4.9 * 7.207^2 = 254.5 m
(Note v2^2 - v1^2 = 70.63^2 - 51.03^2 = 2385 m
2385 / (2 * 9.8) = 122 m (close to 123.1 as was given
Answer:
B. An isothermal compression of an ideal gas.
Explanation:
The internal energy of an ideal gas is just function of the temperature; it does not matter what other thermodynamic property changes, if the temperature does not change, the internal energy neither does. That is just for ideal gases; real gases behaviour is not like that. All of the other options bring with them an increase or decrease of the temperature:
For A, the temperature will decrease because the gas will do work as it expands, converting part of his internal energy to work.
For C, the temperature will increase, because given
, if the volume increases (expansion) and the pressure is constant, the temperature must increase to satisfy the equation.
Answer: Noise above 70 dB can cause hearing damage
Explanation:
By burning the substance, or by digesting it.