First of all, we can calculate the frequency of the photon, which is related to the wavelength by the following equation:
where c is the speed of light and
is the photon wavelength. Substituting into the formula, we find the frequency
Now we can find the energy of the photon with the following equation:
where h is the Planck constant. Substituting numbers, we find
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Useful output = (efficiency) x (input energy)
(1000 J) = (0.12) x (input energy)
Divide each side
by 0.12 : 1,000 J / 0.12 = input energy
Input energy = (8,333 and 1/3) J
Missing part of the text:
"Two masses, m1 = 2.12 kg and m2 = 9.01 kg are on a horizontal frictionless surface and they are connected together with a rope as shown in the figure."
and missing figure (see attachment)
Solution:
We can write Newton's second law for the whole system m1-m2 and for m2 only (2 equations). Only one force (F) acts on the m1-m2 system, while if we consider m2 only we have two forces acting on it: F and T (tension), in the opposite direction. So, the two equations are
where a is the acceleration of the system.
From the first equation we get
and substituting it inside the second equation, we get
re-arranging, we get
Using
,
, and using the maximum value of T that is allowed not to break the rope (T=55 N), we can find the maximum allowed value for F: