Homework Help: Average velocity of bicycle

1. May 30, 2009

tag16

1. The problem statement, all variables and given/known data
A bicycle travels 3.2 km due east in 0.10 h, then 4.7 km at 15.0° east of north in 0.14 h, and finally another 3.2 km due east in 0.10 h to reach its destination. The time lost in turning is negligible. What is the average velocity for the entire trip?
I need to find the magnitude and direction in degrees

2. Relevant equations

average velocity= rf-ri/t1-t2 but there is 3 different times and distances not two...

3. The attempt at a solution

I tried to do vector addition A+B and B+C then add them together but that didn't work to well.

2. May 30, 2009

LowlyPion

You need to resolve the vectors into their x,y components, then determine the total displacement. That will yield your direction.

For average V = |D|/Total time.

Where |D| is the magnitude of your Displacement determined above, where

D = A + B + C

3. May 31, 2009

tag16

I found the initial velocity for x and y by using the formulas 4.7cos(15.0)= 4.539
4.7sin(15.0)= 1.216
delta t=0.10+0.14
Then I found the x and y components by doing: delta rx= vix(delta t)+0= 1.089
delta ry= viy (delta t)-1/2g(delta t)^2=-1.136
Then I added A+B+C for x and y: x=3.2+1.089+3.2=7.48
y=0+.0096+0
Then added them and took the square root. Then divided that number by the total time. Didn't workout to well...

4. May 31, 2009

LowlyPion

Ok. Try this way.

A = 3.2 i + 0 j

B = 4.7*Sin15 i + 4.7*Cos15 j

C = 3.2 i + 0 j