060918

Quiz

1.  A ball rolls from point A to point B, a horizontal displacement of 30 cm, in 1.2 seconds.  It rolls from point A to point C in 2.0 seconds.  The horizontal displacement form point B to point C is 60 cm.  The acceleration between A and B is uniform, as is the acceleration from B to C, and the ball has the same velocity immediately before reaching point B as it does immediately after reaching that point.  Do a complete analysis of the ball’s motion, including a well-labeled graph of v vs. t.

2.  Give your frequency distribution for the 20 quick-click times observed using the TIMER.  The specific instruction in the assigned TIMER analysis was:

What different time intervals did you observe in your first 20 intervals, and how many times did each occur?  List in the box below the different time intervals you observed and the number of times each occurred.  List from the shortest to the longest interval, and use a comma between the time interval and its frequency. 

3. Solve the equation vf^2 = v0^2 + 2 a `ds for `ds, showing the steps of your algebra.    Show also how the units for the resulting expression are identical to the units of `ds.

4.  A ball accelerating uniformly up a ramp reaches a position 10 cm from its starting point at clock time t = .6 seconds, and reaches the position 20 cm from its starting point at clock time t = 1.4 seconds.  The acceleration on the ramp has magnitude 30 cm/s^2.  This means that the acceleration is either -30 cm/s^2 or +30 cm/s^s.

Of the quantities `ds, `dt, v0, vf, a, `dv and vAve, which can be determined directly from the above statement?

What can you then determine directly from these quantities, using the definitions of average velocity and average acceleration, and a v vs. t graph?

What can you determine using the equations of motion?

Lab Computers Access to Network:

The lab computers presently have access to the network site for Room 734.  A subfolder has been created entitled '401'.

To use this folder:

From the lab computers:

Open My Computer from the desktop.

Click on C:\ folder.

Right-click to create a new folder.

Name the folder vhmthphy.

Open the 734 'folder' on the network.

Open the 401 folder.

You will find a text document with important links.  Open it.

You will also find a version of the TIMER program.  Just double-click to run it.

To solve a uniform acceleration problem:

• List the symbols v0, vf, `ds, `dt, a as well as `dv and vAve
• Determine which of these quantities you are given or can immediately determine from the given information.
• List these 'known' quantities at the top of a 'flow diagram'.
• Use the definitions of ave vel and ave accel, along with a v vs. t graph, to figure out everything you can. 

(The v vs. t graph is linear and the average velocity occurs at the middle of the time interval, with v0 and vf at the beginning and the end of the time interval.)

(Use units for every quantity).

• List the equations of motion.
• Circle all the 'known' quantities.
• Find the equations that can be solved for 'unknown' quantities it terms of 'known' quantities. 
• Solve those equations and check that the units work out.
• Substitute the 'known' values (including units) and carefully calculate the 'unknown' values and their units. 
• Make sure the units work.
• Make sure your solutions are consistent.

To analyze today's experiment:

• Analyze the motion from A to B.
• Analyze the motion from B to C.
• Analyze the motion from C back to B.

To 'analyze' means to find the values of all the variables v0, vf, `dt, `ds, a as well as vAve and `dv, using the above procedures.

(unit calculations)

(experiment)

(set up temporary page with paths to sup study etc)