Answer:

Explanation:
If the collision is elastic and exactly head-on, then we can use the law of momentum conservation for the motion of the 2 balls
Before the collision

After the collision

So using the law of momentum conservation


We can solve for the speed of ball 1 post collision in terms of others:

Their kinetic energy is also conserved before and after collision


From here we can plug in 






Answer:
c)
Explanation:
As we know that resultant force is the net force that is acting on the system
As per Newton's II law we know that net force is product of mass and acceleration
so we will have

here we know
m = 80 kg
for circular motion acceleration is given as


now we have



Answer:
Magnification will be equal to 3
Explanation:
We have given focal length of the converging lens 
Focal length of the diverging lens 
Object is placed 40 cm to the length of the converging lens d = 40 cm
Combination of the focal length will be equal to


F = 60 cm
So combination of the focal length will be 60 cm
Magnification is given by

So magnification will be equal to 3
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