#$&*
course Phy 121
The libraries in my area no longer proctor exams. I used my work as a proctor site.
Physics I Major Quiz________________________________________
Completely document your work and your reasoning.
You will be graded on your documentation, your reasoning, and the correctness of your conclusions.
________________________________________
Test should be printed using Internet Explorer. If printed from different browser check to be sure test items have not been cut off. If items are cut off then print in Landscape Mode (choose File, Print, click on Properties and check the box next to Landscape, etc.).
Signed by Attendant, with Current Date and Time: _HB_11/10/10 3 pm _____
If picture ID has been matched with student and name as given above, Attendant please sign here: _HB________
Instructions:
• Test is to be taken without reference to text or outside notes.
• Graphing Calculator is allowed, as is blank paper or testing center paper.
• No time limit but test is to be taken in one sitting.
• Please place completed test in Dave Smith's folder, OR mail to Dave Smith, Science and Engineering, Va. Highlands CC, Abingdon, Va., 24212-0828 OR email copy of document to dsmith@vhcc.edu, OR fax to 276-739-2590. Test must be returned by individual or agency supervising test. Test is not to be returned to student after it has been taken. Student may, if proctor deems it feasible, make and retain a copy of the test..
Directions for Student:
• Completely document your work.
• Numerical answers should be correct to 3 significant figures. You may round off given numerical information to a precision consistent with this standard.
• Undocumented and unjustified answers may be counted wrong, and in the case of two-choice or limited-choice answers (e.g., true-false or yes-no) will be counted wrong. Undocumented and unjustified answers, if wrong, never get partial credit. So show your work and explain your reasoning.
• Due to a scanner malfunction and other errors some test items may be hard to read, incomplete or even illegible. If this is judged by the instructor to be the case you will not be penalized for these items, but if you complete them and if they help your grade they will be counted. Therefore it is to your advantage to attempt to complete them, if necessary sensibly filling in any questionable parts.
• Please write on one side of paper only, and staple test pages together.
Test Problems:
Problem Number 1
If at clock times
• t = 0 s, 5 s and 8 s
an object has velocities
• 8.5 m/s, 10 m/s and 10.25 m/s,
then during each of the two time intervals, 0- 5 seconds and 5 - 8 seconds, approximately how far does it move and at what average rate does its velocity change?
• Show how you could use a graph of velocity vs. time to obtain your results.
• Directly reason out your results using the concept of rate.
• If the automobile is coasting, and if air resistance is not a significant factor, then over which time interval do you think the average slope of the road is greatest?
(0 s, 8.5 cm/s); (5s, 10 m/s); (8 s, 10.25 s)
(10 cm/s – 8.5 cm/s)/(5 s – 0s) = (1.5 cm/s)/(5s) = .3 cm/s^2
‘ds = (10 cm/s + 8.5 cm/s)/2 * (5 s – 0 s)
‘ds = (18.5 cm/s)/2 * 5 s
‘ds = 9.25 cm/s * 5 s
‘ds = 46.25 cm
(10.25 cm/s – 10 cm/s)/(8 s – 5s) = (.25 cm/s)/(3s) = .083 cm/s^2
‘ds = (10.25 cm/s + 10 cm/s)/2 * (8 s – 5 s)
‘ds = (20.25 cm/s)/2 * 3 s
‘ds = 10.125 cm/s * 3 s
‘ds = 231.25 cm
On a graph of velocity vs time, the time would be on the x axis and the velocity would be on the y axis. For each time interval, we could determine the run, rise, and slope. The run is the equivalent of the ‘dt. The rise is the equivalent of the ‘dv. The slope is the rise/run or ‘dv/’dt or acceleration. We can use this data to determine the displacement of each time interval.
If the automobile is coasting, and if air resistance is not a significant factor, the average slope will be in the middle, where there is the greatest change in velocity.
Problem Number 2
A straight ramp is inclined at various slopes.
• The differences in elevation between one end and the other, for the different slopes, are 1.6, 3.2 and 4.8 cm.
• The time required for a cart to coast 87 cm down the ramp, starting from rest, is 3.998996 seconds on the first incline, 1.819538 seconds on the next, and 2.433213 seconds on the last.
How well do the data support the hypothesis that a graph of average acceleration vs. slope will be linear?
The slope indicate that the line will be increasing
Velocity of the three slopes are 21.755461 cm/s, 47.814335 cm/s, and 35.75593 cm/s
The acceleration is 0.250063 cm/s^2, 0.549590 cm/s^2, and 0.410988 cm/s^2.
The line created will not be linear as seen by the increase in the second velocity and acceleration followed by the decrease in the third velocity and acceleration. Our best solution is to use a best fit line with the second line following outside the line.
Problem Number 3
A projectile leaves the edge of a table and, while traveling horizontally at a constant 31 cm/s, falls freely a distance of 58 cm to the floor. If its vertical acceleration is 980 cm/s2, how long does it take to fall and how far does it travel in the horizontal direction during the fall?
vf^2 = v0^2 + 2 a ‘ds
vf^2 = 0^2 + 2 (980 cm/s^2)(58 cm)
vf^2 = 113680 cm^2/s^2
vf = 337.2 cm/s
vAve = (vf + v0)/2
vAve = (337.2 cm/s + 0 cm/s)/2
vAve = (337.2 cm/s)/2
vAve = 168.6 cm/s
‘dt = ‘ds/vAve
‘dt = (58 cm)/( 168.6 cm/s)
‘dt = 0.344 seconds
(31 cm/seconds)(0.344 seconds) = 10.66 cm
Problem Number 4
An object is given an unknown initial velocity up a ramp on which its acceleration is known to have magnitude 15 cm/s^2. It reaches a maximum distance of 120 cm up the ramp before rolling back down.
• What is its initial velocity?
• How many seconds after the initial impetus does the object pass a point 7.8 cm up the ramp from its initial position (give all possible answers)?
a = 15 cm/s^2
vf = 0 cm/s
‘ds = 120 cm
vf^2 = v0^2 + 2 (a)(‘ds)
0 = v0^2 + 2 (15 cm/s^2)(120 cm)
0 = v0^2 + 3600 cm^2/s^2
v0^2 = -3600 cm^2/s^2
v0 = + 60 cm/s
(+60 cm/s)/7.8 or (-60cm/s)/7.8
7.69 seconds or -7.69 seconds
Problem Number 5
What are the average acceleration and final velocity of an object which accelerates uniformly from rest, ending up with velocity 13.9 cm/sec after traveling a distance of 40 cm from start to finish?
v0= 0 cm/sec
vf = 13.9 cm/sec
‘ds = 40 cm
‘ds = (vf + v0)/2 * ‘dt
40 cm = (13.9 cm/s + 0)/2 *’dt
6.95 s = ‘dt
A = (13.9 cm/s – 0)/6.95 s
A= 2 cm/s^2
"
Everything here looks great, but the test must be proctored in an approved proctoring arrangement. I believe I've emailed you about this. Let me know if you didn't get that message.
#$&*