Answer:
66.98 db
Explanation:
We know that

L_T= Total signal level in db
n= number of sources
L_S= signal level from signal source.

= 66.98 db
We get the clearest image if there is no magnification. When we have no magnification the image and real object have the same size.
If we look at the diagram that I attached we can see that:

Two triangles that I marked are similar and from this we get:

The image and the object must have the same height so we get:

This tells how far the screen should be from the lens.
The position of the screen on the optical bench is:
Question 1:
Answer:
The moment of inertia of Alex's rolling hoop is 0.197 
Explanation:
<u>Given</u>:
Mass of the hoop = 0.350 g
Radius of the hoop = 75.0 cm
<u>To Find:</u>
The moment of inertia of Alex's rolling hoop = ?
<u>Solution</u><u>:</u>
The moment of inertia = 
where
m is the mass
r is the radius
Converting cm to m, we get
75.0 cm = 0.75 m
Now substituting the values,
=> moment of inertia = 
=> moment of inertia = 
=> moment of inertia = 
Question 2:
Answer:
The combined angular momentum of the masses is 1.76 
If she pulls her arms in to 0.12 m, her new linear speed is 
Explanation:
Given:
Mass = 2.0 kg
Radius = 0.8 m
Velocity = 1.2 m/s
a.The combined angular momentum of the masses:

Substituting the values,

L= 1.76 
b. If she pulls her arms in to 0.12 m, what is her new linear speed




Answer:

Explanation:
Let's assume that an object is launched straight upward in a gravitational field. Its initial kinetic energy is given by
(1)
where m is the mass and v is the initial speed.
As the object goes higher, its kinetic energy decreases and it is converted into gravitational potential energy, since the total mechanical energy (sum of kinetic and potential energy) must remain constant:

At the highest point of the trajectory, the speed of the object is zero (v=0), so the kinetic energy is also zero (K=0), which means that all the kinetic energy has been converted into potential energy:
(2)
where g is the gravitational acceleration and h is the maximum height of the object.
Due to conservation of energy, we can write that (1) and (2) are equal, so:

from which we can derive an expression for the maximum height reached by the object

Answer:
15m
Explanation:
Hello! first to solve this problem we must find that so much that the tree grew in the 15 years this is achieved by dividing the height of the tree before and after

the tree grew 10 times its initial length in 15 years, so to find how tall the nail is, we multiply this factor by 1.5m
X=(1.5m)(10)=15m
the nail is 15 meters above ground level