Oct. 16 – Newton's Law of Universal Gravitation

First of we discussed the results of the lab I handed back.  Here are some tips for improvement:

Lab Improvements

Only need to show sample calculations.  You don't have to write out the same calculation over and over again for each trial.  Just show the calculations for the first trial.  Do not put calculations in a table.  In a table you should only have numbers with the units at the top.

Units everywhere.  On every number, in the tile of tables, in the middle steps of calculations.  Everywhere.

% difference = precision

% error = accuracy

Don't confuse them.  Ask me if you don't know the difference.

Sources of Error

- Calculations are NOT a source of error.

- Measurement errors.

- Reaction time.

- Friction and other assumptions.

Improvements for Lab

Any improvements should affect your procedures or the equipment. "Measure more precisely," is not an improvement because I already expect you to measure as precisely as you possibly can.

For the next lab...

• independent variable: values that you are changing.
• dependent variable: the value that responds to the change, what you are measuring.
• controlled variable: what you tried to keep constant.

Then the next topic...

Newton's Law of Universal Gravitation

Here are some examples of what gravitational field might look like if we could see it:

The lines show how objects might move when they fly past the Earth.

If the little dot in the middle is the Earth, these vectors show the gravitational force at different locations around the Earth.

Another way to illustrate what a field might do.

Finally, here's what people use to represent the gravitational field around a black hole:

The gravitational field affects all areas of space.  The only way you can avoid feeling the effects is if you're in free, such as in this ride:

The brief moment when you are falling is what it would feel like there were no gravitational field.  You can also get the same effect if you were in an airplane that is diving.  We call the effect weightlessness.  Here are some videos of what that would look like:

Here's what it would look like to pop water balloons in a weightless environment:

Instead of an airplane, you could also go to the international space station to experience weightlessness.