M = mass of the girl = 53.4 kg 
m = mass of skateboard = 3.55 kg 
V' = velocity of the combination of girl and skateboard before she jumps forward = 0  
 
V = velocity of the girl forward = 1.32  
 
v = velocity of the skateboard afterward = ?
Using conservation of momentum 
(M + m) V' = MV + m v 
inserting the values 
(53.4 + 3.55) (0) = (53.4) (1.32) + (3.55) v 
v = - 19.86  
 
 
        
             
        
        
        
Answer:
v = 8.8 m /s 
Explanation:
For listener and source going away from each other the formula of Doppler effect is as follows 

V is velocity of sound , v is velocity of listner and source of sound 
f₀ is apparent frequency and f is real frequency 
V = 343 , v = ? ,f = 210 , f₀ = 221
Put these value in the relation above 
![[tex]\frac{210}{221} = \frac{343-v}{343+v}](https://tex.z-dn.net/?f=%5Btex%5D%5Cfrac%7B210%7D%7B221%7D%20%3D%20%5Cfrac%7B343-v%7D%7B343%2Bv%7D) [/tex]
[/tex]
v = 8.8 m /s 
 
        
             
        
        
        
It’s burning wax. All of the other options are physical changes .
        
             
        
        
        
Kinetic energy = (1/2) (mass) x (speed)²
At 7.5 m/s, the object's KE is (1/2) (7.5) (7.5)² = 210.9375 joules
At 11.5 m/s, the object's KE is (1/2) (7.5) (11.5)² = 495.9375 joules
The additional energy needed to speed the object up from 7.5 m/s 
to 11.5 m/s is (495.9375 - 210.9375) = <em>285 joules</em>.
That energy has to come from somewhere. Without friction, that's exactly 
the amount of work that must be done to the object in order to raise its 
speed by that much.
        
             
        
        
        
Nicolaus Copernicus was the one who brought astronomy out of the dark ages.
 In one of his books "On the Revolutions of the Heavenly Bodies", he published the renowned line which declares his theory.
Nicolaus Copernicus, A polish astronomer put forward the theory that the is th Sun one that rests in the middle or center of the Universe and the planet Earth revolves around it on its axis every day.which was considered to be called the Heliocentric system.
To know more about the Heliocentric system refer to the link brainly.com/question/3491738?referrer=searchResults.
To know about Sir Nicolaus Copernicus' work refer to the link brainly.com/question/6699117?referrer=searchResults.
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