Answer:
C. -12 ab
Explanation:
The restoring force on a spring is given by Hooke's law:

where
k is the spring constant
x is the stretched (or compressed) displacement of the spring
In this problem we have:
k = 4a
x = 3b
Substituting into the equation, we find:

And the negative sign means that the direction of the force (negative) is opposite to the direction of the displacement (positive).
 
        
             
        
        
        
Acceleration is the
rate of change of velocity, a body moving with uniform velocity does not
possess acceleration at all i.e. acceleration is zero
 
        
             
        
        
        
Stars form from an accumulation of gas and dust, which collapses due to gravity and starts to form stars. Stars are typically classified by their spectrum in what is known as the Morgan-Keenan or MK system.
        
             
        
        
        
If both waves have the same wavelength, then the amplitude of 
their sum could be anything between 1 cm and 9 cm, depending 
on the phase angle between them.
If the waves have different wavelengths, then the resultant is a beat 
with an amplitude of 9 cm.