Gravity Lab Introduction Name Date Block Introduction: In this lab, computer simulation, we will investigate the factors that effect gravitational force. We know that in order to feel or see the effects of gravity a very large mass is required. 1. Go to http://phet.colorado.edu/en/simulation/gravity-force-lab 2. Select RUN NOW. (You may have to download it. You might also try and see if it will run in HTML 5. Your instructor might tell you which is better.) Note: The force will be a very small number. To make taking the data easier we will only look at the last six digits. In the example to the right we would record the force as 003,963 nanonewtons or 3,963 nn. Qualitative Observations: (circle correct answer for 1-6) Prediction: In this part of the lab you will be moving the masses closer together and farther apart. You will also be increasing and decreasing the masses while keeping the distance constant. Make a prediction as to what you think will happen as your change the distance: Distance predication: Mass prediction: (circle correct answer for 1-6) 1. Move the masses closer. When they move closer the force between them becomes (Greater/Less/the same) 2. Move the masses further apart. When the masses move away the force between them becomes (Greater/Less/the same) 3. Double Mass 1. When mass 1 is doubled the force between them becomes (Greater/Less/the same) 4. Cut Mass 2 in half. When the mass is reduced the force between them becomes (Greater/Less/the same) 5. In any of the situations did the forces on the two masses ever differ in magnitude? (Yes / No) 6. In any of the situations did the forces on the two masses ever not point in opposing directions? (Yes / No) 7. What physics LAW explains questions 5 and 6 (either give name or definition)
Quantitative Data Collection: Part I: MASS It is now time to build a model. First, let us examine the relationship between masses. Separate Mass 1 and Mass 2 so that their centers of mass (black dots) are 6 meters apart. Set Mass 2 to 30.0 kg. Start Mass 1 at 0 kg. Increasing the mass each time with 1 kg and collect the data for gravitational force until you have 10 data points. 0 kg 1. Sketch a graph. Note: Gravitational force is the dependent variable (Y axis) and Mass 1 being independent (X axis). (A blank graph is at the end of this packet.) 2. Redo the experiment but set Mass 1 to 30.0 kg and vary Mass 2. You will collect data on Mass 2 s relationship to force. Analysis: (USE COMPLETE SENTENCES AND REPHRASE THE QUESTIONS) 1. Does it matter which mass increases? 2. What type of relationship is there between Mass and force? (Use the following sentence: As mass increases, gravity. ) 3. Are mass and gravitational force proportional or inversely proportional to each other?
Part II: DISTANCE Let us examine the relationship between masses. Set both masses to 30.0 kg. Collect 10 data points of different distances between the masses. Note you can move the ruler and the masses to maximize your range. 1. Sketch a graph of vs. Distance (F vs. d) Analysis: 1. What is the relationship between distance and the force of gravity? (Use the following sentence: As distance increases, gravity. )
Optional Challenge: -Sketch a graph of vs. 1/ Distance (F vs. 1/d) -Sketch a graph of vs. 1/ Distance squared (F vs. 1/d 2 ) 1. What is the actual relationship between distance and the force of gravity? 2. See if you can write out the proportions between Mass 1 (m 1 ), Mass 2 (m 2 ) distance (r) to the of gravity (F g ). F g Check with your instructor to make sure your proportionality (combination of (m 1 ), (m 2 ) and (r)) is correct. If you are correct, you should notice entering lab data for m 1, m 2, and r does not equal F g. Also work out your units, do they equal a Newton? This means there is also a constant (G) that we need to multiply to our proportionality to complete our formula. 3. Make a graph of vs. your proportionality; this will help determine your constant (G) 4. Determine the gravitational constant (G) that will multiply to your units. Give k its proper unit too. Hint, all your units combined need to = a Newton. G= 5. Write your full formula and check with your instructor. Congratulations!
vs Mass 1 (nanonewtons) vs Distance (nanonewtons)