# Average speed & average velocity Problem

1. Oct 3, 2007

### davidco

1. The problem statement, all variables and given/known data
Brandon is climbing a mountain. He starts from an elevation of H1=511m above sea level. In 6.18 hours he climbs to an elevation of H2=2746m above sea level. The length of his path is L1=16000m.

A)What is the average angle of ascent the path makes with the horizontal?Theta=
B)What is his average speed along the path in meters/second? average speed=
C)What is his average vertical velocity? Vup=
D)After he eats he hikes back down to their starting point in T2=4.24 hours
What is his average vertical velocity? Vdown=

2. Relevant equations
avg speed=total distance/total time
avg velocity=v=Delta x/delta t

3. The attempt at a solution

Im so confused as to what equations to use.

B)avg speed= total distance/total time

16000M/22680S=0.705m/s

C)avg velocity=v=Delta x/delta t

D)Confused on D as well

Please give some suggestions or the correct equations will be great.thanx Dave

2. Oct 4, 2007

### hotvette

You are on the right track. If you haven't done it already, one thing that helps is to draw a picture.

For a, you have the correct equation. Hint: what does L1 represent in a simple idealized geometric shape?

For c & d: be careful. The problem says average vertical velocity.

Also, looks like you double posted by mistake.

Last edited: Oct 4, 2007
3. Oct 4, 2007

### davidco

Hotvette thanx alot for the help just got a few more questions.

If your talking in terms of a triangle L1 would represent my hypotenuse I believe. So would 16000m be my hypotenuse is what your suggesting. But dont I have to choose the equation involving the hypotenuse to find the angle. Like:

sin theta= opp/hyp
or

But my question is what is the equation for vertical velocity?

Thanx Vette

4. Oct 4, 2007

### learningphysics

For the angle yes, use:

sin theta = opp/hyp

average vertical velocity = vertical displacement/time

5. Oct 4, 2007

### davidco

Thank you learn,

But im wondering if my hyp=16000m and im trying to find theta. whats my opp or how do i find my opp.?

6. Oct 4, 2007

### learningphysics

What distance does he travel vertically? they give you initial height and final height...

7. Oct 4, 2007

### davidco

Thanx Learn,

Ok so if I subtract the H2=2746m- 511m=my distance is 2235m

So to find theta I did this:

sin theta=opp/hyp

sin theta=2235m/16000
theta=7.98 degrees or 8 degrees

Please tell me this is correct

8. Oct 4, 2007

### learningphysics

yup, looks right to me. But I get 8.03 degrees.

9. Oct 4, 2007

### davidco

Thanx,

For my average speed =total distance/total time,do I use the 16000m for total distance/6.18hrs or do i convert hrs to seconds. Since my answer has to be in m/s?

10. Oct 4, 2007

### learningphysics

Yeah, I think converting to s is best. otherwise your answer will be in m/hr... best to use m/s.

11. Oct 4, 2007

### davidco

Question so if vertical speed= deltaV/T,would my deltaV= .705m/s?I got .705m/s from my average velocity equation which was 16000m/22680s=.705m/s for avgV. Is average vertical velocity and vertical velocity the same equation?

12. Oct 4, 2007

### learningphysics

vertical velocity is vertical displacement which you know is 2235m divided by time.