Ineed ! it's for a class i'm failing!

you exert 375 j to move a 45-kg object 5 m. how much force is required?
a. 1,875n
b. 75n
c. 420n
d. 225n

Here's the formula you need to remember:

                        Work = (force) x (distance)

That's it.  It's so short and simple that you didn't pay much attention
to it when it came around the first time.  I KNOW it's in your notes,
maybe several pages back.  Now, you should memorize it, before
it gets away from you again.

                          Work = (force) x (distance).

Say it with me:   "Werk eekwals forss timez distanss". 

Now that you have that tool in your toolbox, we can go on
and look at the question.

This question is not easy, and when I read it carefully, I DON't
think that's because there's a lot of Physics hidden in it.  I think
it's because whoever wrote the question was unclear on some
of the concepts, and wrote a poor question.

The question DOESN't tell you what direction I moved the 45-kg
object.  Did I slide it across the floor, or did I lift it straight up ?

Now I'm thinking about it some more, and I changed my mind.
NOW I think the question was written by a person who made it
very sneaky, to see if we know what we're doing.

Close your eyes and tell me the formula for work that we just
memorized. . . . . . Very Good !   Work = (force) times (distance).

From the question, we know the work, and we know the distance.

                                                     375 J                      = (force) x (5 meters)

Divide each side by (5 meters):   (375 J) / (5 meters) = Force

                                                          Force = 75 newtons . 

That bit about "45 kg" is just there to confuse us.  We don't care
WHAT the mass of the object is.  We don't need it to answer the
question, and we don't need to know it.  I almost got sucked in,
and I was trying to take you down with me.

All we need to know is:      Work = (force) times (distance) .

Answer(b) both involve the use of levers;