# Work question (involving vectors)

• May 20th 2010, 12:21 PM
sj9110
Work question (involving vectors)
I can't seem to get the correct answer for this problem. I'm not sure where i'm going wrong.

"A tow truck drags a stalled car along a road. The chain makes an angle of 30° with the road and the tension in the chain is 1100 N. How much work is done by the truck in pulling the car 1 km?"

• May 20th 2010, 12:38 PM
AllanCuz
Quote:

Originally Posted by sj9110
I can't seem to get the correct answer for this problem. I'm not sure where i'm going wrong.

"A tow truck drags a stalled car along a road. The chain makes an angle of 30° with the road and the tension in the chain is 1100 N. How much work is done by the truck in pulling the car 1 km?"

Work = (Force x Distance)

Have you considered decomposing your chain into a right angle triangle with the road (i.e. 1100 N is the hypotenuse)?

I don't have a caclulator on me but this should be relatively simple, once you find the component along the road multiply by the distance (i.e. 1km).

Also note, the answer will depend on if the Truck is accelerating or not. If it is, we need to involve work-energy theorem but if not, the above should suffice.
• May 20th 2010, 12:54 PM
sj9110
yeah, i think my error is in the rounding. it says to the nearest ten thousand. I did 1100cos(30) = 952.6279442 = F

W = 952.6279442 (D) (Where D = 1000) (converting km to m)
W = 952627.9442

The answer I gave (incorrectly) was 953,000.. now I see this is only to the thousand, not ten thousand, so I guess it should be 950,000.

If someone could confirm this I would be very grateful, I only get one more chance at it.

Thanks.