Answer:

Explanation:
When we push the box from the bottom of the incline towards the top then by work energy theorem we can say that
Work done by all the forces = change in kinetic energy of the system

here we know that

also we know that the length of the incline is given as

now we have

so we have

The resultant vector can be determined by the component vectors. The component vectors are vector lying along the x and y-axes. The equation for the resultant vector, v is:
v = √(vx² + vy²)
v = √[(9.80)² + (-6.40)²]
v = √137 or 11.7 units
A = Delta v/Delta t
Delta v = 25 - 0 = 25
Delta t = 30
25/30 = 5/6 = 1.66 repeating
I don't know what you mean when you say he "jobs" the other ball, and the answer to this question really depends on that word.
I'm going to say that the second player is holding the second ball, and he just opens his fingers and lets the ball <u><em>drop</em></u>, at the same time and from the same height as the first ball.
Now I'll go ahead and answer the question that I've just invented:
Strange as it may seem, <em>both</em> balls hit the ground at the <em>same time</em> ... the one that's thrown AND the one that's dropped. The horizontal speed of the thrown ball has no effect on its vertical acceleration, so both balls experience the same vertical behavior.
And here's another example of the exact same thing:
Say you shoot a bullet straight out of a horizontal rifle barrel, AND somebody else <em>drops</em> another bullet at exactly the same time, from a point right next to the end of the rifle barrel. I know this is hard to believe, but both of those bullets hit the ground at the same time too, just like the baseballs ... the bullet that's shot out of the rifle and the one that's dropped from the end of the barrel.