Answer:
I think the answer is C/ Tell me If you got it right
Answer:
A. K = 0.546 eV
B. cooper and iron will not emit electrons
Explanation:
A. This is a problem about photoelectric effect. Then you have the following equation:
(1)
K: kinetic energy of the ejected electron
Ф: Work function of the metal = 2.48eV
h: Planck constant = 4.136*10^{-15} eV.s
λ: wavelength of light = 410nm - 750nm
c: speed of light = 3*10^8 m/s
As you can see in the equation (1), higher the wavelength, lower the kinetic energy. Then, the maximum kinetic energy is obtained with the lower wavelength (410nm). Thus, you replace the values of all variables :

B. First you calculate the energy of the photon with wavelengths of 410nm and 750nm

You compare the energies E1 and E2 with the work functions of the metals and you can conclude:
sodium = 2.3eV < E1
cesium = 2.1 eV < E1
cooper = 4.7eV > E1 (this metal will not emit electrons)
iron = 4.5eV > E1 (this metal will not emit electrons)
Answer:
2.17 Mpa
Explanation:
The location of neutral axis from the top will be

Moment of inertia from neutral axis will be given by 
Therefore, moment of inertia will be
![\frac {240\times 25^{3}}{12}+(240\times 25)\times (56.25-25/2)^{2}+2\times [\frac {20\times 150^{3}}{12}+(20\times 150)\times ((25+150/2)-56.25)^{2}]=34.5313\times 10^{6} mm^{4}}](https://tex.z-dn.net/?f=%5Cfrac%20%7B240%5Ctimes%2025%5E%7B3%7D%7D%7B12%7D%2B%28240%5Ctimes%2025%29%5Ctimes%20%2856.25-25%2F2%29%5E%7B2%7D%2B2%5Ctimes%20%5B%5Cfrac%20%7B20%5Ctimes%20150%5E%7B3%7D%7D%7B12%7D%2B%2820%5Ctimes%20150%29%5Ctimes%20%28%2825%2B150%2F2%29-56.25%29%5E%7B2%7D%5D%3D34.5313%5Ctimes%2010%5E%7B6%7D%20mm%5E%7B4%7D%7D)
Bending stress at top= 
Bending stress at bottom=
Mpa
Comparing the two stresses, the maximum stress occurs at the bottom and is 2.17 Mpa
Answer:
The horizontal distance is 4.823 m
Solution:
As per the question:
Mass of man, m = 65.0 kg
Height of the hill, H = 5.00 m
Mass of the backpack, m' = 20.0 kg
Height of ledge, h = 2 m
Now,
To calculate the horizontal distance from the edge of the ledge:
Making use of the principle of conservation of energy both at the top and bottom of the hill (frictionless), the total mechanical energy will remain conserved.
Now,
where
KE = Kinetic energy
PE = Potential energy
Initially, the man starts, form rest thus the velocity at start will be zero and hence the initial Kinetic energy will also be zero.
Also, the initial potential energy will be converted into the kinetic energy thus the final potential energy will be zero.
Therefore,
where
v = velocity at the hill's bottom
Now,
Making use of the principle of conservation of momentum in order to calculate the velocity after the inclusion, v' of the backpack:



Now, time taken for the fall:



Now, the horizontal distance is given by:
x = v't = 
The Newton’s law that explains why the hands get red when you press them hard against a wall is Newton’s third law. When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite direction on the first body.