Question

A constant force F=8i+5j−7k moves an object along a straight line from point (3, -6, -6) to point (-4, -8, 9).

Find the work done if the distance is measured in meters and the magnitude of the force is measured in newtons.

Answer 1

@e.mccormick can you take a look?

Answer 2

OK. So, you know your distance formula for this?

Answer 3

Well I know w = F • D

So what I have done is found that f = (8,5,-7) and D = (-4, -8, 9) - (3, -6, -6) = (-7,-2,15)

so I took (-7,-2,15) • (8,5,-7) = -59 but thats seems to be wrong

Answer 4

Ah, you did d wrong.

\(d(p,q)=\sqrt{(p_1-q_1)^2+(p_2-q_2)^2+\ldots+(p_n-q_n)^2}\)

Answer 5

Then again... I didn't do physics, so if you got the other from a formula. I learned vectors through linear algebra. Hehe.

Answer 6

Well this isnt physics just calc 3. Ill give it a shot

Answer 7

I was looking at this: http://answers.yahoo.com/question/index?qid=20110907173249AA6wkZV

Answer 8

Ah, may be a good shortcut:
http://en.wikipedia.org/wiki/Dot_product

Answer 9

"Mechanical work is the dot product of force and displacement vectors."

Answer 10

So displacement rather than distance.

Answer 11

And that would be the right one then.

Answer 12

they way i did it would be the right one?

Answer 13

Yes, because you found the displacment and they gave you force. As long as you did the do produc correctly, that would work.

Answer 14

I did the math wrong. its -171

Answer 15

Yah. I just found that myself.

Answer 16

Thanks again

Answer 17

np. Dot product has some really interesting uses.