Rockets are able to accelerate in space because: a. they have excess fuel to burn from their initial take-off c. the force of gravity propels them b. they push exhaust in the same direction as they wish to accelerate d. they push exhaust in a direction opposite to the direction that they wish to accelerate

d. they push exhaust in a direction opposite to the direction that they wish to accelerate

Explanation:

This is a consequence of Newton's third law (action-reaction law), which states that

"When an object A exerts a force on an object B (action), object B exerts and equal and opposite force on object A (reaction)"

In this case, we can think the rocket as object A and the exhaust as object B. The rocket pushes the exhaust in a certain direction,applying a force on it; as a result of Newton's third law, the exhaust exerts the same force but on opposite direction on the rocket. Therefore, the rocket is pushed by the exhaust in the opposite direction, and therefore it accelerates because of this force.

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.