An apple hanging from a limb has potential energy because of its height . if it falls ,what becomes of this energy just before its hits the ground ? when it hits the ground?

Just before its hits the ground it becomes kinetic energy and when it hits the ground it becomes in another form of energy (acoustic energy or thermal energy, for example)

Explanation:

Energy is the ability of matter to produce work in the form of movement, light, heat, among others.

In this sense, according to the Conservation of Energy principle: "energy is not created or destroyed, it is transformed."

So, in the case of the apple, its total energy is conserved.

When the apple is hanging from a limb, it has zero kinetic energy (because it is at rest) and has gravitational potential energy , which depends on the mass , the acceleration due gravity and the height :

When the apple falls, just before its hits the ground, this gravitational potential energy transforms in kinetic energy (since the apple is moving), which depends on the mass and velocity of the apple:

When the apple hits the ground, the gravitational potential energy is zero (h=0) and the kinetic energy transforms into some other form of energy (acoustic energy or thermal energy, for example).

learn it on the intertant so you can solve

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.