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50N is your force and the acceleration is -9.8m/s^2 due to gravity. 
So, you just plug that in. 

BUT you know that mass cannot be negative, so you just disregard the negative sign and the mass of the rock is 5.102 grams.
 
        
             
        
        
        
Forces that are equal in size but opposite in direction and do not cause a change in an object's movement are called balanced forces.
forces that aren't equal in size and do cause a change in movement (what it seems like you're asking for) are called UNBALANCED FORCES 
so answer (in case that wasn't clear, as I'm tired) : unbalanced forces 
        
             
        
        
        
Answer: P= W/t so P=50/20 =2.5 W
 
        
             
        
        
        
If valence electron i.e electron from 3s orbital is removes, sodium will have configuration same as Neon with a +1 charge on it.
Hence charge on the ion will be +1.
        
                    
             
        
        
        
Answer:
= 8
Explanation:
noise from power mower = 106 dB
noise from rock concert = 115 dB
we would be applying the formula for the decibel level of sound to get the intensities.
 (B) = 10 log \frac{I}{I₀}
I = intensity of sound
I₀= reference intensity = 10^{-12} W/m^{2}
- intensity of the power mower
 
106 = 10 log \frac{I}{10^{-12}} 
10.6 =  log \frac{I}{10^{-12}} 
10^{10.6} = \frac{I}{10^{-12}} 
I = 10^{10.6} x 10^{-12}
I of power mower = 0.0398 W/m^{2}
- intensity of the rock music
 
115 = 10 log \frac{I}{10^{-12}} 
11.5 =  log \frac{I}{10^{-12}} 
10^{11.5} = \frac{I}{10^{-12}} 
I = 10^{11.5}  x 10^{-12}
I of rock music = 0.316 W/m^{2}
now the ratio of the intensity of the rock music to the power mower
 = \frac{0.316}{0.0398}
= 8