Answer:
The force of friction acting on block B is approximately 26.7N. Note: this result does not match any value from your multiple choice list. Please see comment at the end of this answer.
Explanation:
The acting force F=75N pushes block A into acceleration to the left. Through a kinetic friction force, block B also accelerates to the left, however, the maximum of the friction force (which is unknown) makes block B accelerate by 0.5 m/s^2 slower than the block A, hence appearing it to accelerate with 0.5 m/s^2 to the right relative to the block A.
To solve this problem, start with setting up the net force equations for both block A and B:

where forces acting to the left are positive and those acting to the right are negative. The friction force F_fr in the first equation is due to A acting on B and in the second equation due to B acting on A. They are opposite in direction but have the same magnitude (Newton's third law). We also know that B accelerates 0.5 slower than A:

Now we can solve the system of 3 equations for a_A, a_B and finally for F_fr:

The force of friction acting on block B is approximately 26.7N.
This answer has been verified by multiple people and is correct for the provided values in your question. I recommend double-checking the text of your question for any typos and letting us know in the comments section.
Answer:
The number of atoms in the unit cell is 2, the crystal structure for the alloy is body centered cubic.
Explanation:
Given that,
Weight of metal A = 12.5%
Weight of metal B = 87.5%
Length of unit cell = 0.395 nm
Density of A = 4.27 g/cm³
Density of B= 6.35 g/cm³
Weight of A = 61.4 g/mol
Weight of B = 125.7 g/mol
We need to calculate the density of the alloy
Using formula of density

....(I)
Where, n = number of atoms per unit cells
m = Mass of the alloy
V=Volume of the unit cell
N = Avogadro number
We calculate the density of alloy


We calculate the mass of the alloy


Put the value into the equation (I)

Hence, The number of atoms in the unit cell is 2, the crystal structure for the alloy is body centered cubic.
Its B: reduce the amount of energy needed to do the work by putting the work onto something else
The body shivers to produce energy and it uses the energy to keep it warm. The body would stop shivering when it has produced enough energy to keep it warm and the atmosphere around it has got warmer
Answer: 1.22 m
Explanation:
The equation of motion in this situation is:
(1)
Where:
is the final height of the ball
is the initial height of the ball
is the vertical component of the initial velocity (assuming the ball was thrown vertically and there is no horizontal velocity)
is the time at which the ball lands
is the acceleration due gravity
So, with these conditions the equation is rewritten as:
(2)
(3)
Finally:
