The number of lines per mm in the diffraction grating is 326.
<h3>What is diffraction grating?</h3>
A diffraction grating is a type of optical instrument obtained with a continuous pattern. The pattern of the diffracted light by a grating depends on the structure and number of elements present.
The given data in the problem is
is the angle formed between the path of the incident light and the diffracted light = 9. 2°
λ is the wavelength of the light=490nm=4.9
N is the number of lines per mm in the diffraction grating=?
n is ordered = 1
The formula for the diffraction grating is;

The number of lines per mm is found as;

Hence the number of lines per mm in the diffraction grating is 326.
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Modelling the structure of the atom is important because modeling replaces the real system with something similar but easier to examine. Option B
<h3>What is modeling?</h3>
A model is a representation of reality. We know that a model could help us to recreate reality in a manner that we could be able to relate fully with it. A model could be used also a means of explanation.
The atomic models that we have usually help us to understand more abut the atom. Therefore, modelling the structure of the atom is important because modeling replaces the real system with something similar but easier to examine. Option B
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Complete Question:
The elastic energy stored in your tendons can contribute up to 35 % of your energy needs when running. Sports scientists have studied the change in length of the knee extensor tendon in sprinters and nonathletes. They find (on average) that the sprinters' tendons stretch 43 mm , while nonathletes' stretch only 32 mm . The spring constant for the tendon is the same for both groups,
. What is the difference in maximum stored energy between the sprinters and the nonathlethes?
Answer:

Explanation:
Sprinters' tendons stretch, 
Non athletes' stretch, 
Spring constant for the two groups, k = 31 N/mm = 3100 N/m
Maximum Energy stored in the sprinter, 
Maximum energy stored in the non athletes, 
Difference in maximum stored energy between the sprinters and the non-athlethes:

Explanation:
The increase in the body temperature of pronghorn, the fastest North American animal, results from the chemical energy of the pronghorn converting into kinetic energy with efficiency less than 100%. The remaining energy is converted into heat energy. Thus, raising the temperature of pronghorn.
Due to the chemical energy it gains both kinetic and heat energy.
Fill in the fraction: 3,600/90 = 40; turn it into a unit fraction.
40 mi/min