Answer:
 C) 16.3 ml
Explanation:
Density is equal to the ratio between the mass of an object and its volume:

where
m is the mass
V is the volume
In our problem, we know:
- density of aluminium: 
- mass of the aluminium foil: 
So we can re-arrange the equation above and use these data to find the volume of the piece of aluminium foil:

 
        
             
        
        
        
Answer:
   f = 276.6 Hz
Explanation:
This musical instrument can be approximated to a tube system where each tube has one end open and the other closed.
In the closed part there is a node and in the open part a belly or antinode. Therefore the wavelength is
           L = λ/ 4
speed is related to wavelength and frequency
           v = λ f
           λ = v / f
we substitute
           L = v / 4f
           f = v / 4L
the speed of sound at 20ºC is
           v = 343 m / s
let's calculate
           f =  
           f = 276.6 Hz
 
        
             
        
        
        
Answer:
Say a 14 year old girl was at a construction site and she was asked to move something like a 10,000 pound brick( one brick). She would be acting on it as the unbalanced force but they would still not change their position.
so to say the girl would be doing everything she could to move that brick but the brick would still be in that same spot so the unbalanced force (the girl) would be acting on the thing that was at rest but it wouldn't move.
so the unbalanced force would not really be acting on the thing at rest; even though the unbalanced force was doing something to the brick.
( just think about it and you will eventually get it...just imagine in your head...)
Explanation:
 
        
             
        
        
        
The magnitude is doubled. The direction doesn't change.
        
             
        
        
        
Answer:
Potential energy only 
Explanation:
at the top of its swing the pendulum stops moving , (therefore it has no KINETIC energy)  thus all of the energy is stored as potential energy.