Since the stone is travelling, the displacement cannot be constant. This leaves the last 2 choices as possibilities. Now consider the acceleration that can act on the stone. Acceleration due to gravity is the only one. That means the horizontal component of the stone has to be constant since there is no acceleration in the horizontal direction.
Answer:
Explanation:
Given
initial velocity component of engines is


time period of engine running=763 s
Displacement in 

Using
in x and y direction




In y direction




x component
y component
If net external force acting on the system is zero, momentum is conserved. That means, initial and final momentum are same → total momentum of the system is zero.
Answer:
The group that remains unaltered is called the control group.
If you give it unbalanced force it would go up and if you can't give it enough it will stay a balanced force