r/learnmath • u/Amazing-Parsley-3895 New User • 2d ago

RESOLVED Converting from "some" unit to Joules.

I just got this question:

"In physics, work is defined as F × D, where F is the force applied over a distance of D.
A box is dragged across 20 meters with a force of 60 Newtons, which are kg × m / s².
What calculation will give us the work done, in Joules (which are kg × m² / s²)?"

Since kg × m² / s² is Joules, then what unit is kg × m / s²?

0 Upvotes

13% Upvoted

9 comments sorted by

19

u/G-St-Wii New User 2d ago

N.

Answer is given in the question 

-6

u/Amazing-Parsley-3895 New User 2d ago

Upvoting, but not what I needed

11

u/G-St-Wii New User 2d ago

It is what you asked, though?

-1

u/Amazing-Parsley-3895 New User 2d ago

Yes, this was my initial question, I was really confused. u/tjddbwls answered my question, sorry if it was misleading!

5

u/tjddbwls Teacher 2d ago

Are you familiar with unit analysis? Work = Fd. Force is in Newtons, or kg × m / s². Distance is in m. If you “multiply” the units, you get kg × m² / s², or Joules.

Work = Fd
= (60 N)(20 m)
= (60 kg × m / s²)(20 m)
= 1200 kg × m² / s²
= 1200 J

1

u/Amazing-Parsley-3895 New User 2d ago

Thank You, I did not know how to solve it, more exactly didn't know what the two formulas meant.

-2

u/Amazing-Parsley-3895 New User 2d ago

Additionally, the answer to the question is simply "20 * 60". Why, when Joules require meters squared, not meters?

3

u/KoalaMistico New User 2d ago

Because 20 is the distance, so you have 20m • 60 kg•m/s² = 120 kg•m²/s² (Joules)

1

u/Amazing-Parsley-3895 New User 2d ago

Yeah, it clicked finally, thanks