Answer:
A-the energy of the wave decreases gradually
Explanation:
when a wave is acted upon by an external damping force the energy of the wave decreases gradually.
The energy degrades into the form of heat which is considered to be of less value and use. The reason is because it disperses and spreads more widely.
So therefore it end up as heat with a little sound but that is close to none because that too disperses into heat i.e. decreased form of energy.
Answer:
The number of crates is 84580.
Explanation:
mass, m = 30 kg
height, h = 0.9 mm
Power, P = 0.5 hp = 0.5 x 746 W = 373 W
time, t = 1 minute = 60 s
Let the number of crates is n.
Power is given by the rate of doing work.

Answer: Option (A) is the correct answer.
Explanation:
Laser helps in zooming an image on which it is directed or falls so that it becomes easier for a large population to understand what the teacher or guide is talking about.
For example, when Greg is giving slide show presentation to a large audience then in order to make his slides visualized by everyone in the room he uses laser.
Therefore, we can conclude that a laser best help him with the presentation as he can use the laser to enlarge images on the slides.