Answer:
Part a)

Part b)

Explanation:
As we know that there is no external force on the system of two masses so here total momentum of the system will remains conserved
so we can say




Part b)
magnitude of the initial speed of A = 
magnitude of the initial speed of B = 
magnitude of final speed of A = 
magnitude of final speed of B = 
Now change in total kinetic energy is given as



 
        
             
        
        
        
Let the first car's average speed be x
The second car's speed would be x+5




So the speed of the slower car is 50mph, and the speed of the faster car is 55mph
 
        
        
        
Answer:
 1800J
Explanation:
Given parameters: 
Weight of the book  = 20N 
Total distance covered  = 45m + 15m + 30m  = 90m 
Unknown: 
Total work performed on the books  = ? 
Solution: 
To solve this problem we must understand that work done is the force applied to move a body through a certain distance. 
 So; 
     Work done  = Force x distance 
   Work done  = 20 x 90  = 1800J
 
        
             
        
        
        
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