Answer:
Grow up man, this is completely based on your curriculum, we would need your book to answer, and this has to be done by you.
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All waves must ____ have to travel through
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Explanation:
Wave
It is the periodic disturbance in a medium.
Types of Wave
There are two types of wave in general depending upon their propagation through a substance.
• Mechanical
• Electromagnetic
Mechanical Wave
It is the kind of wave which needs medium to travel. For example: Sound Wave
That means sound can be heard only whenever there is presence of certain substance like water, glass, air etc .It can’t be heard in vacuum no matter how loud is the sound.
Electromagnetic Wave
Is that which can travel through medium as well as through vacuum. For example: Light
But unlike sound, light can be seen through a substance or in vacuum. That is the reason it is referred as electromagnetic wave.
Answer:
U² = 142.86 N
U¹ = 357.14 N
Explanation:
Taking summation of the moment about point A, we get the following equilibrium equation: (taking clockwise direction as positive)

where,
W = weight of boy = 500 N
U² = reaction ay B = ?
Therefore,

<u>U² = 142.86 N</u>
Now, taking summation of forces on the plank. Taking upward direction as positive, for equilibrium position:

<u>U¹ = 357.14 N</u>
Sure, if the mortality (death) rate is even higher than the birth rate.
Because sound waves don't travel through the vaccume of space. Hope this helped