# Homework Help: Average Speed/Velocity

1. Aug 29, 2011

### ugkwan

A honeybee leaves the hive, flies in a straight line to a flower 6 km away in 10 min, and then takes 10 minutes to return (also in a straight line).

a.) Please find the distance travelled and displacement for the entire trip:
distance travelled:
I know the distance total is 12 km

displacement: 0

b.) Please find the average speed and average velocity for the entire trip:
average speed:
This is where I get confused. Total distance/rate of change in meters = Average speed. This would mean the speed is undefined.

average velocity:
Same confusion because the algebra would mean this question is undefined with a displacement of zero.

2. Aug 29, 2011

### KingNothing

Velocity = distance / time. As long as your time is not zero, it is defined. It's only the denominator that needs to be non-zero.

The average speed is the total distance traveled divided by total time spent traveling.

The velocity is similar, only it involves the total distance traveled in a direction - that is, the velocity on the way back will be the same as on the way out, only negative.

3. Aug 31, 2011

### ugkwan

Thanks for the correction. I now see that I had the formula wrong. So it is displacement over time, and time is 20 minutes. So velocity is 0/20 and speed is 12/20.

4. Sep 2, 2011

### Lobezno

That is correct, but they're funny units (kilometres per minute?).

To change to a more physics-y, SI unit, try metres per second:

(12km*1000 m km^-1)/(12mins*60 s min^-1)

=12000/720= whatever it is.

5. Sep 2, 2011

### Galron

They do that deliberately: that is phrase the question in unweildy units, this makes you render more applicable units by the simple fact of expedience.