The formation of new volcanoes and the eruption of some existing ones already.
Answer:
Convex lens and convex mirrors are similar that
1. They have the same image characteristics at various object positions
2. They possess a positive focal length
3. Both their ray lines converge to a particular focal point
Answer:
Average recoil force experienced by machine will be 200 N
Explanation:
We have give mass of each bullet m = 50 gram = 0.05 kg
There are 4 bullets
So mass of 4 bullets = 4×0.05 = 0.2 kg
Initial speed of the bullet u = 0 m/sec
And final speed of the bullet v = 1000 m/sec
So change in momentum 
Time is given per second so t = 1 sec
We know that force is equal to rate of change of momentum
So force will be equal to 
So average recoil force experienced by machine will be 200 N