C.
Explanation: Because mirrors are lighter, and they are easier than lenses to make perfectly smooth.
Answer:

Explanation:
From frequency of oscillation

Initially with the suspended string, the above equation is correct for the relation, hence

where k is force constant and m is the mass
When the spring is cut into half, by physics, the force constant will be doubled as they are inversely proportional

Employing f2/ f1, we have

Answer:
9.81N
Explanation:
the force of attraction is given by
F=<u>GmM</u><u>/</u><u>R²</u><u> </u>
where m is mass of the body
M is mass of the earth
R is radius of the earth
G is the universal gravitational constant(6.67x10-¹¹)
hence we substitute the values in the formula.
<em> </em><em>you</em><em> </em><em>can</em><em> </em><em>ask</em><em> </em><em>questions</em>
At 10 m/s, it will take
(2 m)/(10 m/s) =
0.2 sto bridge the gap.
_____
However, it will take an additional 0.514 seconds (0.714 s total) for the policeman to land on the building below. The answer depends on the meaning of the question.
The total mechanical energy of the block-spring system is given by the sum of the potential energy and the kinetic energy of the block:

where
k is the spring constant
x is the elongation/compression of the spring
m is the mass of the block
v is the speed of the block
At the point of maximum displacement of the spring, the velocity of the block is zero: v=0, so the kinetic energy is zero and the mechanical energy is just potential energy of the spring:

(1)
where we used x=A, the amplitude (which is the maximum displacement of the spring).
Since we know
A = 11.0 cm= 0.11 m
E = 1.10 J
We can re-arrange (1) to find the spring constant: