Answer:
In this case, the particles of the medium move parallel to the direction that the pulse moves. This type of wave is a longitudinal wave.
A method of investigation in which a problem is first identified and observations, experiments, or other relevant data are then used to construct or test hypotheses that purport to solve it.
Answer:
20 J
Explanation:
Given:
Weight of the book is, 
Height or displacement of the book is, 
The work done on the book to raise it to a height of 2 m on a shelf is against gravity. The gravitational force acting on the book is equal to its weight. Now, in order to raise it, an equal amount of force must be applied in the opposite direction.
So, the force applied by me should be equal to weight of the body and in the upward direction. The displacement is also in the upward direction.
Now, work done by the applied force is equal to the product of force applied and displacement of book in the direction of the applied force.
Therefore, work done is given as:

Therefore, the work done to raise a book to a height 2 m from the floor is 20 J.
Answer:
Speed of the wave is 7.87 m/s.
Explanation:
It is given that, tapping the surface of a pan of water generates 17.5 waves per second.
We know that the number of waves per second is called the frequency of a wave.
So, f = 17.5 Hz
Wavelength of each wave,
Speed of the wave is given by :
v = 7.87 m/s
So, the speed of the wave is 7.87 m/s. Hence, this is the required solution.