The mass of the planet Jupiter is 318 times the mass of Earth and its radius is 10.0 times the radius of the Earth.
a) What is your weight on Jupiter?
b) What force do you exert on Jupiter?
c) A 120. kg space probe approaches Jupiter. What acceleration due to gravity does it experience when it is 10 000. km above the “surface” of the planet?
Here's the solution:
Then I showed some full solutions to the challenging questions from previous handouts:
For Period 2:
Here's the solution to Newton's 3rd Law Handout question #6.
For Period 5:
Here's the solution to Physics Worksheet question #10.
Good luck in your studying, see you on Monday for the test!
First of we discussed the results of the lab I handed back. Here are some tips for improvement:
Lab Improvements
Only need to show samplecalculations. 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.
Today we did some examples and then went over the lab for tomorrow.
Look at this image...
Can you explain how this sprinkler works using Newton's Laws?
According to Newton's 3rd Law, every action has an equal and opposite reaction. The sprinkler pushes the water out sideways and the water pushes the sprinkler in the opposite direction, therefore the sprinkler spins around.
Read this Manga to if you want some more explanation about Newton's 3rd Law
Here's quick review and demo of Newton's Second Law:
Next we talked about Newton's 3rd Law. I did a demo with a rolling chair. Here are the notes:
Newton's 3rd law may be easy to write down, but it's can be tricky to understand. Here are more videos that demonstrate the law:
How do water jetpacks work? Heres'a diagram:
The jetpack forces water down, the reaction force is the water pushing the person up. If the upwards force is greater than gravity, the person will accelerate upwards.
Here are more examples of Newton's 3rd Law:
Every time you walk, you are using Newton's 3rd Law! You push the ground backwards and the ground pushes you forwards!
Homework
Follow the unit plan and do the homework for day 4.
The tendency for an object to keep moving (or stay motionless).
Inertia is directly related to mass. More mass means more inertia.
There were two
space probes launched in 1977 called Voyager 1 and Voyager 2.They have no rockets and no source of
propulsion on board.They are now
over 18 billion km away. Here's a tracker from NASA http://voyager.jpl.nasa.gov/where/
What will happen to them?
Since there is no forces acting on them, they will keep going due to Newton's First Law.
An object in motion tends to stay in motion unless acted upon by an external force.
In fact, they will keep going forever unless they encounter something to exert a force on them. In the space between our sun and other starts, there's really not much that will stop them!
Here's an image taken by Voyager:
The tiny speck in the beam on the right is the Earth!
Here's what Carl Sagan had to say about this image:
From this distant vantage point, the Earth
might not seem of any particular interest. But for us, it's different. Consider
again that dot. That's here. That's home. That's us. On it everyone you love,
everyone you know, everyone you ever heard of, every human being who ever was,
lived out their lives. The aggregate of our joy and suffering, thousands of
confident religions, ideologies, and economic doctrines, every hunter and
forager, every hero and coward, every creator and destroyer of civilization,
every king and peasant, every young couple in love, every mother and father,
hopeful child, inventor and explorer, every teacher of morals, every corrupt
politician, every "superstar," every "supreme leader,"
every saint and sinner in the history of our species lived there – on a
mote of dust suspended in a sunbeam.
On Earth, we also see Newton's First Law in action all the time:
A force from the tires stops the bike, but this force doesn't act on the rider, so he keeps going!
The same is true for cars. If there's not enough friction to stop a car, say on an icy road for instance, cars will have a difficult time stopping:
Using inertia, can you explain how this works?
Possible solution:
When the card is flicked, a force acts on the card. No addition force is applied to the coin (small bit of friction), therefore, due to inertia, the coin remains motionless. Once the card is removed, there is no longer a normal force on the coin, the net force is gravity, causing the coin to fall into the cup.
Homework
You can now do the homework from Day 1 and Day 2 of the unit plan.
