Sir Isaac Newton was among the first to observe the movement of objects and express those observations as laws. According to Newton's law of inertia, a body a. in variable motion will remain in motion unless its state of matter changes.

b. with no kinetic energy will remain along a path with a constant radius.

c. with a variable potential energy will remain with a constant, nonzero acceleration.

d. in uniform motion will remain in motion unless it is acted upon by an outside force

it's D

Explanation:

Newton's first law of motion states that a body at rest remains at rest or if in motion remains in motion at a constant velocity unless acted upon by a external 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.

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.