SCI109 The Cosmos

Activity 3 – Newton’s Second Law and Motion

Reference:

Go to masteringastronomy.com; click Study Area/Self-guided Tutorial – Motion and Gravity

There are two parts for this activity. You will work on both parts described below and also comment on one other student’s work.

The first part is to learn how a net force causes acceleration, described by Newton’s second law F = ma.

Read the Introduction and Objectives to understand the concept. In Lesson 1, you will see this simulation page:

[pic]

Play with this simulation by choosing three different masses (AVOID CHOOSING THE SAME MASS USED BY OTHER STUDENTS) . By clicking the button “Push”, you will produce a speed vs time graph (do it for three different masses), and then use F = ma to calculate the acceleration for each mass. Record the mass and acceleration values in the table below:

|Mass 1 = 120 |a1 =.83 (100/120) |
|Mass 2 = 180 |a2 =.55 (100/180) |
|Mass 3 =300 |a3 =.33 (100/300) |

Now you should have three straight lines in the graph. Each calculated acceleration should represent the slope of the corresponding line.

Take a screen-shot of your graph image and then paste it here。 Use your graph to determine the slopes and compare it with three acceleration values in your table. [pic]

The second part is study Newton’s universal gravitational law:

F = G M1 M2 / R2

Your weight is the force that the planet attracts you, i.e.

Your weight = mg where g = G M2 / R2

In which G is universal