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Assoli18 [71]
3 years ago
6

Light of 1.5 ✕ 1015 hz illuminates a piece of tin, which has a work function of 4.97 ev. (a) what is the maximum kinetic energy

of the photoelectrons?
Physics
1 answer:
stiks02 [169]3 years ago
8 0
In the photoelectric effect, the energy of the incoming photon (E=hf) is used in part to extract the photoelectron from the metal (work function) and the rest is converted into kinetic energy of the photoelectron:
hf = \phi + K
where
h is the Planck constant
f is the frequency of the incident light
\phi is the work function of the material
K is the kinetic energy of the photoelectron.

The photoelectron generally loses part of its kinetic energy inside the material; however, we are interested in its maximum kinetic energy, that is the one the electron has when it doesn't lose energy, so we can rewrite the previous equation as
K_{max} = hf - \phi

The work function is (in Joule)
\phi = (4.97 eV)(1.6 \cdot 10^{-19} J/eV)=7.95 \cdot 10^{-19} J

and using the data of the problem, we find the maximum kinetic energy of the photoelectrons
K_{max} = (6.6 \cdot 10^{-34} Js)(1.5 \cdot 10^{15} Hz)-7.95 \cdot 10^{-19}J= 1.95 \cdot 10^{-19} J

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Three masses (3 kg, 5 kg, and 7 kg) are located in the xy-plane at the origin, (2.3 m, 0), and (0, 1.5 m), respectively.
Artist 52 [7]

Answer:

a) C.M =(\bar x, \bar y)=(0.767,0.7)m

b) (x_4,y_4)=(-1.917,-1.75)m

Explanation:

The center of mass "represent the unique point in an object or system which can be used to describe the system's response to external forces and torques"

The center of mass on a two dimensional plane is defined with the following formulas:

\bar x =\frac{\sum_{i=1}^N m_i x_i}{M}

\bar y =\frac{\sum_{i=1}^N m_i y_i}{M}

Where M represent the sum of all the masses on the system.

And the center of mass C.M =(\bar x, \bar y)

Part a

m_1= 3 kg, m_2=5kg,m_3=7kg represent the masses.

(x_1,y_1)=(0,0),(x_2,y_2)=(2.3,0),(x_3,y_3)=(0,1.5) represent the coordinates for the masses with the units on meters.

So we have everything in order to find the center of mass, if we begin with the x coordinate we have:

\bar x =\frac{(3kg*0m)+(5kg*2.3m)+(7kg*0m)}{3kg+5kg+7kg}=0.767m

\bar y =\frac{(3kg*0m)+(5kg*0m)+(7kg*1.5m)}{3kg+5kg+7kg}=0.7m

C.M =(\bar x, \bar y)=(0.767,0.7)m

Part b

For this case we have an additional mass m_4=6kg and we know that the resulting new center of mass it at the origin C.M =(\bar x, \bar y)=(0,0)m and we want to find the location for this new particle. Let the coordinates for this new particle given by (a,b)

\bar x =\frac{(3kg*0m)+(5kg*2.3m)+(7kg*0m)+(6kg*a)}{3kg+5kg+7kg+6kg}=0m

If we solve for a we got:

(3kg*0m)+(5kg*2.3m)+(7kg*0m)+(6kg*a)=0

a=-\frac{(5kg*2.3m)}{6kg}=-1.917m

\bar y =\frac{(3kg*0m)+(5kg*0m)+(7kg*1.5m)+(6kg*b)}{3kg+5kg+7kg+6kg}=0m

(3kg*0m)+(5kg*0m)+(7kg*1.5m)+(6kg*b)=0

And solving for b we got:

b=-\frac{(7kg*1.5m)}{6kg}=-1.75m

So the coordinates for this new particle are:

(x_4,y_4)=(-1.917,-1.75)m

5 0
3 years ago
ONLINE CALCULATOR .A force of 187 pounds makes an angle of 73 degrees 36 ' with a second force. The resultant of the two forces
saul85 [17]

Answer:

The magnitudes of the second force is   Z = 129.9 N

The magnitudes of the  resultant force is   R = 256.047 N

Explanation:

From the question we are told that  

    The force is  F = 187 \ lb

     The angle made with second force \theta_o = 73 ^o 36' =  73 + \frac{36}{60}  =  73.6^o

     The angle between the resultant force and the first force \theta _1  = 29 ^o 1 ' = 29 + \frac{1}{60}  = 29.0167^o

For us to solve problem we are going to assume that

     The magnitude of the second force is  Z N

     The magnitude of the resultant force is R N

According to Sine rule

                \frac{F}{sin (\theta _o - \theta_1 }  = \frac{Z}{\theta _1}

Substituting values

             \frac{187}{sin(73.3 - 29.01667)} =\frac{Z}{sin (29.01667)}  

             267.82 =\frac{Z}{0.4851}  

              Z = 129.9 N

According to cosine rule

       R = \sqrt{F ^2 + Z^2 + 2(F) (Z) cos (\theta _o) }

Substituting values

     R = \sqrt{187^2 + 129.9 ^2  + 2 (187 ) (129.9) cos (73.6)}

     R = 256.047 N

 

3 0
3 years ago
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