Data:
Vo = 120 ft / s
α = 30°
t = 5 s
x = ?
Formulas:
cos(α) = Vo,x / Vo => Vo,x = Vo * cos(α)
x = Vo,x * t
Calculations:
Vo,x = 120 ft / s * cos(30) = 103.92 ft /s
x = 103.92 ft/s * 5 s = 519.6 ft
Answer: 519.6 ft
It allows the light to pass through but no other object can
Answer:
83.2 W/m^2
Explanation:
The radiation per unit area of a star is directly proportional to the power emitted, which is given by Stefan-Boltzmann law:

where
is the Stefan-Boltzmann constant
A is the surface area
T is the surface temperature
So, we see that the radiation per unit area is proportional to the fourth power of the temperature:

So in our problem we can write:

where
is the power per unit area of the present sun
is the temperature of the sun
is the power per unit area of sun X
is the temperature of sun X
Solving for I2, we find

Answer:
Electrons are influenced by internal forces.
-On the temperature, density of electrons per unit of volume and relaxation time.
-The temperature
Explanation:
The Drude model neglects interactions between electrons and ions and with themselves. Those interactions (by which we refer as electromagnetic forces) influence in the random movement and freedom of the electron. So, they could be more restricted or could influence in conductivity more.
The deduction of the resistivity comes from the Ohm's law, which states that the Electric field in the material is proportional to the current density of electrons by a constant, which is the resistivity itself. The equation goes as follows:

Where e refers to electron (or the charge of it), τ is the relaxation time (average time between collisions), m is the mass and n is the density of charges (electrons in this case) per volume. However, experimentally resistivity is also dependent on temperature, which actually influence the relaxation time. The thermal energy influence in the behavior of the electrons, making them collide with phonons, have more randomness and reduced mean free path.
Answer:
The near point of an eye with power of +2 dopters, u' = - 50 cm
Given:
Power of a contact lens, P = +2.0 diopters
Solution:
To calculate the near point, we need to find the focal length of the lens which is given by:
Power, P = 
where
f = focal length
Thus
f = 
f =
= + 0.5 m
The near point of the eye is the point distant such that the image formed at this point can be seen clearly by the eye.
Now, by using lens maker formula:

where
u = object distance = 25 cm = 0.25 m = near point of a normal eye
u' = image distance
Now,



Solving the above eqn, we get:
u' = - 0.5 m = - 50 cm