# Acceleration of skier on slope

1. May 13, 2007

### never-enough21

This might be an extremely easy question and I'm just over-thinking it, but could someone give me a hand with some grade 10 physics?

1. A downhill skier has an initial speed of 2.5 m/s. She accelerates up to a speed of 20 m/s in 3.8 s.

a) Calculate the average acceleration of the skier.

Okay, so I know that acceleration equals velocity over time, but I'm slightly confused. So I know how to calculate the acceleration of 20 m/s in 3.8 s. Which is ... (about) 5.26. But, I get stuck here.

Last edited: May 13, 2007
2. May 13, 2007

### hage567

Why are you confused? Explain.

3. May 13, 2007

### never-enough21

I don't know how to find the average acceleration.

Last edited: May 13, 2007
4. May 13, 2007

### never-enough21

wait, is that all I have to do?

5. May 13, 2007

### hage567

No, your answer isn't correct. Average acceleration is the change in velocity over a given time interval. So what's the velocity at the beginning of your time interval, and what is it at the end?

Do you recognize this: $$a_{ave} = \Delta v / \Delta t$$

6. May 13, 2007

### DAKONG

$$a_{ave} = \frac{\Delta v}{\Delta t} = \frac {v_{final} - v_{initial} }{t_{final} - t_{initial} }$$

it is definition

Last edited: May 13, 2007