Answer:
 -15 m/s
Explanation:
The computation of the velocity of the 4.0 kg fragment is shown below:
For this question, we use the correlation of the momentum along with horizontal x axis
Given that
Weight of stationary shell = 6 kg
Other two fragments each = 1.0 kg
Angle = 60
Speed = 60 m/s
Based on the above information, the velocity = v is 



= -15 m/s
 
 
        
             
        
        
        
It has to be the last one because whenever lights are turned on it decreases because all lights are on at the same time. It's good to just have one light on. It doesn't use as much electricity.
        
             
        
        
        
Answer:
lambda = 343 m/s divided by 340 Hz = 1.009 seconds
Hope it helps and have a wonderful day!