What is the Work Done by Air Resistance on a Round Trip?

[emerica1254]

Homework Statement

A bicyclist rides 1.32 km due east, while the resistive force from the air has a magnitude of 6.12 N and points due west. The rider then turns around and rides 1.32 km due west, back to her starting point. The resistive force from the air on the return trip has a magnitude of 6.12 N and points due east. Find the work done by the resistive force during the round trip

Homework Equations

W=(fcosΘ)s

The Attempt at a Solution

6.12*cos180*1.32+6.12*cos180*1.32= -16.14, but this is not the right answer

 

[tiny-tim]

hi emerica1254!

6.12*cos180*1.32+6.12*cos180*1.32= -16.14, but this is not the right answer

looks right to me

have you tried -16.1 J ?

 

[emerica1254]

hi emerica1254!


looks right to me

have you tried -16.1 J ?

Still didn't work and i have only one more chance to get it right, so if anyone else knows what I'm doing wrong i would appreciate it

 

[p21bass]

Well, there's two possible things I see.

1) The problem states that the distance is 1.32 km. You should convert this to meters.

2) Or, possibly, they are looking for net force. In which case, as a vector sum, -8078 in one direction plus +8078 in the opposite direction would equal zero.

I'm thinking they really want it done the first way, though.

 

[emerica1254]

Well, there's two possible things I see.

1) The problem states that the distance is 1.32 km. You should convert this to meters.

2) Or, possibly, they are looking for net force. In which case, as a vector sum, -8078 in one direction plus +8078 in the opposite direction would equal zero.

I'm thinking they really want it done the first way, though.

Converting to m worked thanks for all your help.