Answer:
The equivalent stiffness of the string is 8.93 N/m.
Explanation:
Given that,
Spring stiffness is





According to figure,
 and
 and  is in series
 is in series
We need to calculate the equivalent
Using formula for series


Put the value into the formula


k and  is in parallel
 is in parallel
We need to calculate the k' 
Using formula for parallel

Put the value into the formula


 ,k' and
,k' and  is in series
 is in series
We need to calculate the equivalent stiffness of the spring
Using formula for series

Put the value into the formula


Hence, The equivalent stiffness of the string is 8.93 N/m.
 
        
             
        
        
        
Seismic wave is the answer
        
             
        
        
        
Answer:
ma = 48.48kg
Explanation:
To find the mass of the astronaut, you first calculate the mass of the chair by using the information about the period of oscillation of the empty chair and the spring constant. You use the following formula:
 (1)
      (1)
mc: mass of the chair
k: spring constant = 600N/m
T: period of oscillation of the chair = 0.9s
You solve the equation (1) for mc, and then you replace the values of the other parameters:
 (2)
    (2)
Next, you calculate the mass of the chair and astronaut by using the information about the period of the chair when the astronaut is sitting on the chair:
T': period of chair when the astronaut is sitting = 2.0s
M: mass of the astronaut plus mass of the chair = ?
 (3)
  (3)
Finally, the mass of the astronaut is the difference between M and mc (results from (2) and (3)) :

The mass of the astronaut is 48.48 kg
 
        
             
        
        
        
Answer:
J
Explanation:
The daughter moves with greater acceleration backwards because of her weight.
 
        
                    
             
        
        
        
Hello.
The answer is <span>remains the same.
</span>The total amount of energy stays the same because the 1st Law of Thermodynamics states that energy can neither be created nor destroyed, it can only change forms. <span>So the chemical energy is just being converted into heat and light.
</span>
Have a nice day