Answer:
a)
& 
b) 
c) 
Explanation:
Given:
mass of the book, 
combined mass of the student and the skateboard, 
initial velocity of the book, 
angle of projection of the book from the horizontal, 
a)
velocity of the student before throwing the book:
Since the student is initially at rest and no net force acts on the student so it remains in rest according to the Newton's first law of motion.

where:
initial velocity of the student
velocity of the student after throwing the book:
Since the student applies a force on the book while throwing it and the student standing on the skate will an elastic collision like situation on throwing the book.

where:
final velcotiy of the student after throwing the book
b)



c)
Since there is no movement of the student in the vertical direction, so the total momentum transfer to the earth will be equal to the momentum of the book in vertical direction.



Answer:
B. has a smaller frequency
C. travels at the same speed
Explanation:
The wording of the question is a bit confusing, it should be short/long for wavelength and low/high for frequency. I assume low wavelength mean short wavelength.
All sound wave travel with the same velocity(343m/s) so wavelength doesn't influence its speed at all. It won't be faster or slower, it will have the same speed.
Velocity is a product of wavelength and frequency. So, a long-wavelength sound wave should have a lower frequency.
The option should be:
A. travels slower -->false
B. has a smaller frequency -->true
C. travels at the same speed --->true
D. has a higher frequency --->false
E. travels faster has the same frequency --->false
Um you should putting it in a object that it can fill then go from there
Answer:
Explanation:
Correct order of energy of energy states within an atom is as follows
1s , 2 s, 2 p 3 s ,3 p, 4s , 3d, 4p, 4p,5s etc.
There is discrepancies in this order due to overlapping of outer orbitals with inner orbitals so sometimes outer orbitals have lower energy.
Because its expose to the wires inside that could electrify you.