Answer:
wrong statement :  Momentum is not conserved for a system of objects in a head-on collision.
Explanation:
 In a head on collision of two objects , two equal and opposite forces are created at the point of collision . These two forces create two impulses in opposite direction which results in equal and opposite changes in momentum in each of them . Hence net change in momentum is zero. In this way momentum is conserved in head on collision of two objects. 
 
        
             
        
        
        
 Answer:
Average speed is 60 km/hour
Explanation:
When we need to calculate average speed, we use this equation:

Where:    position at the beginning
   position at the beginning
                at the end
   at the end
               
               
Then:     
               
Finally    V = 60 km/hour
 
        
             
        
        
        
Answer:
The self-induced emf in this inductor is 4.68 mV.
Explanation:
The emf in the inductor is given by:

Where:
dI/dt: is the decreasing current's rate change = -18.0 mA/s (the minus sign is because the current is decreasing)
L: is the inductance = 0.260 H 
So, the emf is:

Therefore, the self-induced emf in this inductor is 4.68 mV.    
I hope it helps you!
 
        
             
        
        
        
Answer:
The mutual speed immediately after the touchdown-saving tackle is 4.80 m/s
Explanation:
Given that,
Mass of halfback = 98 kg
Speed of halfback= 4.2 m/s
Mass of corner back = 85 kg
Speed of corner back = 5.5 m/s
We need to calculate their mutual speed immediately after the touchdown-saving tackle
Using conservation of momentum

Where,  = mass of halfback
= mass of halfback
 =mass of corner back
=mass of corner back 
 = velocity of halfback
= velocity of halfback
 = velocity of corner back
= velocity of corner back
Put the value into the formula



Hence, The mutual speed immediately after the touchdown-saving tackle is 4.80 m/s
 
        
             
        
        
        
The EMF of the battery includes the force to to drive across its internal resistance. the total resistance:  
R = internal resistance r + resistance connected rv 
R = r + rv  
Now find the current:  
V 1= IR 
I = R / V1  
find the voltage at the battery terminal (which is net of internal resistance) using  
V 2= IR  
So the voltage at the terminal is:  
V = V2 - V1  
This is the potential difference vmeter measured by the voltmeter.