I think it would be at 3 or 6 but I would go with 3 not really sure tho
Answer:

Explanation:
From the question we are told that:
Mass 
Height 
Speed 
Angle 
Generally the equation for K.E is mathematically given by
Since
The potential energy and kinetic energy is equal to the kinetic energy as it hits the ground.
Therefore



Answer:
I would use a propeller like the first or second just from my experience. Just play around with the different ones and see which one works best for you.Don't make the propeller too thick or thin or else it may not work.
Explanation:
Have a great day! Good luck!
Answer:
a.
Explanation:
cuz whenever the ball was traveling up the staircase it was building up energy to use (potential energy) unlike b.