I believe it is the first one
        
             
        
        
        
Answer:
The  velocity is  
Explanation:
From the question we are told that 
    The  mass of the bullet is  
     The initial speed of the bullet is  
    The mass of the target is  
     The  initial velocity of target is  
     The  final velocity of the bullet is  is  
     
Generally according to the law of momentum conservation we have that 
       
=>   
=>    
 
        
             
        
        
        
Answer:D
Explanation: i found the answer in an answer key! 
 
        
             
        
        
        
Answer:
The same pendulum could be adjusted to have the same period, in the equator must have a length of 3.949m.
Explanation:
Tnp= 4 sec
gnp= 9.83 m/sec²
Lnp= 3.97m
Tequ= 4 sec
gequ= 9.78 m/sec²
Lequ=?
Lequ= (Lnp* gequ) / gnp
Lequ= 3.949 m