The use of force to move an object is called work. This only applies if the object moves.
<u>Answer:</u>
Submarines use a device called Periscope that uses the concept of multiple reflections and help us see objects above the water surface.
<u>Explanation:</u>
When a light ray falls on a reflecting surface like a mirror, it gets reflected. In multiple reflections, the incident light ray is made to reflect multiple times by arranging the reflecting surfaces in different ways.
In submarines, we use Periscope, which is a long tube like structure. The long tube is bent at ends. It uses two simple mirrors which are placed parallel to each other at an angle of 45 degrees. The light from one mirror gets reflected to the other mirror, thus causing a multiple reflection.
Answer:
12.5752053801 m/s

No.
Explanation:
Q = Volume flow rate = 
d = Diameter of pipe = 9 cm
A = Area = 
Volume flow rate is given by

Velocity of fluid is 12.5752053801 m/s
The volume flow rate in m³/s is 
The flow of fluid does not depend on the type of water used. Hence the answers would be same. If Q is constant v will be the same irrespective of the type of water used.
1 atmospheric pressure = 760.0 mm Hg
Thus 580 mm Hg = (580 mm Hg/(760 mm Hg/atm))
= 0.763 atm