No it is a chemical change
Answer:
I reckon towards b. Let me know if im right
Answer:4-strikes the plane at same time as the other body
Explanation:
Given
If both bodies is falling on a horizontal plane and second body is given an acceleration in horizontal direction then it does not change the time to reach the Horizontal Plate as there is no change in vertical direction.
Horizontal acceleration will give only horizontal range and horizontal velocity.
Answer:
Part a)

Part b)

Part c)

Explanation:
Part a)
As we know that the friction force on two boxes is given as



Now we know by Newton's II law

so we have




Part b)
For block B we know that net force on it will push it forward with same acceleration so we have




Part c)
If Alex push from other side then also the acceleration will be same
So for box B we can say that Net force is given as




Answer: Not 100% sure but I believe the answer is B.
Hope this helps! ^^