# Homework Help: Terminal velocity of a steel ball

1. Nov 16, 2005

### sueanne

Hi I doing a coursework on finding the terminal velocity of a steel ball in a liquid at different temperatures

How is my graph suppose to like? My two variables are temperature and terminal velocity (i got my terminal velocity from speed = distance / time)
And if possible, if you know it, what will the line look like? Is it porportional?

2. Nov 16, 2005

### Tide

What does the graph from your data look like?

3. Nov 16, 2005

### sueanne

I have temperature on the x axis, and terminal velocity on the y axis. My line is linear, and i think its porportional like a 45 degree line, except the last point which must be an anomalie

4. Nov 16, 2005

### Pengwuino

These weren't experimentally determined were they...

5. Nov 16, 2005

### sueanne

sorry mate i dont understand what ure on about 'experimentally determind" of course my results are inaccurate. the actual formula for finding terminal velocity is way more complex than that , but my teacher insisted on it man.

6. Nov 16, 2005

### Tide

Depending on how you made your measurements, that last point may reflect a situation where the ball hadn't reached terminal velocity - just a guess.

7. Nov 16, 2005

### sueanne

Yeah I guess so, whats really weird about the whole thing is that the whole experiment was based on a programme, we just had to time the steel ball reaching the bottom

8. Nov 20, 2005

### polyperson

Increase in temperature lowers the viscosity

Terminal velocity = (2 / 9) (r² g / η) (ρ - ρ')

Where r=radius, g=gravity, η=viscosity, ρ= density of steel, ρ'=density of the liquid

So, if η decreases, velocity increases.