Calculating Average Velocity for a Bike Ride

[mkylman]

Homework Statement

You ride your bike for 1.5h @ avg velocity of 10km/h, then for 30min @ 15km/h
What is you average velocity?

So I think that the variables are this

V_f=15km/h(.000004m/s)
V_i=10km/h(.000003m/s)
T_f=90m(5400s)
T_f=30m(1800s)

Homework Equations

That's what I'm asking -_-

I think that it is

V[sub]avg[/sub] = d[sub]f[/sub] - d[sub]i[/sub]
       ------
       t[sub]f[/sub] - t[sub]i[/sub]

The Attempt at a Solution

everything I try I get gross decimal numbers -_- Isn't there an easier way?

 

[Dick]

0.000004m/sec is nothing like 15km/hr. I hope you are not using that. Just work in km and hr. You got the right equation though. How far did you travel in all and how long did it take you in all? The quotient is the average velocity.

 

[mkylman]

so to get the total distance I'd have to do

d = t/v

1.5h/10kmh = 15km
.5h/15kmh = 7.5km
overall d = 22.5km
overall t = 2h

so my average velocity is

v = d/t
v = 22.5km/h
    --------
       2h
v = 11.25km/h

^ that?

 

[Dick]

^ That! But I've never seen anyone write / for multiplication before. Don't you mean like 1.5hr*10km/hr=15km?

 

[mkylman]

yeah my bad -_- I hadn't realized it til afterwards; I have no idea what I was typing ^_^

Thank you so much man!