Speed can be defined as
a. acceleration divided by time.
b. change in position divided by change in time.
c. change in time divided by change in position.
d. change in velocity divided by change in time.
awnser is a

Speed can be defined as

Explanation: B because if you think about it, 50 milers per hour means they are dividing the time it takes to drive a certain distance going that speed. So id has to be answer B! your welcome. Please upvote only if its correct!

iron would move it is magnetic there is a mag field around the current in the wire

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.