Vector components - displacement

[shawli]

Homework Statement

A train moving at a constant speed of 100km/h travels east for 40min, then 30^o east of north for 20 min, and finally west for 30min. What is the train's average velocity for the trip?

Homework Equations

The Attempt at a Solution

I think I have to calculate displacement from the given velocities, using vector components for 100km/h [30^o E of N]. Then I find the total x displacement and total y displacement and divide by time (1.5h) to find the x and y velocities. I'm not sure what to do after this :S.

 

[Doc Al]

Then I find the total x displacement and total y displacement and divide by time (1.5h) to find the x and y velocities.

That will give you the components of the average velocity. Find the magnitude of that vector.

 

[shawli]

Oh , I have to use Pythagorean theorem to find the resultant vector, right?

I divide that value by 1.5hr.

And finally I can find the direction by using the arctangent of the displacement components?

I end up getting 29.4 km/h [41 degrees north of east] , but I'm not sure if it's correct since I haven't been given answers to the problem.

 

[Doc Al]

Oh , I have to use Pythagorean theorem to find the resultant vector, right?

I divide that value by 1.5hr.

And finally I can find the direction by using the arctangent of the displacement components?

That's right.

I end up getting 29.4 km/h [41 degrees north of east] , but I'm not sure if it's correct since I haven't been given answers to the problem.

Looks good to me!

 

[shawli]

Thanks a ton!