| Chapter 3: Do listed problems. | ||||||||||
| Simulations | ||||||||||
| ANSWERS | ||||||||||
| Quiz 3 | ||||||||||
| 1 | 2 | 3 | 6 | 7 | 10 | 13 | 14 | 18 | 20 | 23 |
| Helpers!! Click this link then click the links "Practice Questions" and "Practice Problems" in the left hand column. |
| SCROLL DOWN TO THE BOTTOM OF THE PAGE FOR AN EXPLANATION OF THE GRAPHING HANDOUTS |
| Go to masterinphysics.com for assignment 1 on "Motion Part 1" from Quiz 1. |
| Click here for 3,000 Solved Problems in Physics (Schaum's Solved Problems Series) |
| PLEASE REGISTER YOUR EMAIL AT THE BOTTOM OF THE PHYSICS 4A PAGE . SCROLL DOWN THAT PAGE TO FIND THE EMAIL REGISTRATION FORM !!! REGISTER AGAIN EVEN IF YOU HAVE ALREADY DONE SO; THE DATABASE HAS BEEN REFRESHED! |
| error log #1--- Note the correction to problem 18: the vector in the original axes system should read (-Bcos30, Bsin30). ie. note the minus sign on the x-component. |
| 1. See class notes; this exercise was done in recent lab session; thanks for all your work ! |
| 2. This can be done with a ruler and
protractor: Find the ratio of the magnitudes of the two vectors by
directly measuring them on the page with a centimeter scale
ruler. Call this ratio A/B. Let your scale be 1 unit =
4 cm. Then you might draw vector-B with magnitude 2 units, i.e. 8
cm. Then you would get A = (8 cm)·(A/B) for vector-A's
magnitude drawn on your paper.
Of course the angles are measured with your protractor. No scale is
required for that measurement. |
| 3. (a) Ex = Ecos(theta) Ey = Esin(theta), Note theta is the angle with the x- axis. Now use your basic trigonometry skills to find both components with respect to the other angle. Use the properties of the sine and cosine of complimentary angles. The second angle, with the y-axis, is the compliment of the first because they add to 90 degrees. |
| 6. (a) This vector points in Quadrant 4. Thus rx = 100cos45 and ry = -100sin45. (b) Points in Quadrant 1. Thus both components are positive. (c) The x - component of this vector is zero. The y component is -a·sin90, where a is the magnitude. |
| 7.
(a) The y - component of this vector is zero. The x component
is -v·cos0. |
| 18. This problem can be done "manually
" or using a formula for the transformation of vectors,
including displacements (x,y) from the origin. Read on.
Manually: x'2 + y'2 = x2 + y2 and Bx'2 + -By'2
= Bx2 + By2 |
| 10.
(a) Here's a hint to get you started on the other parts. Vector -B
points in Quadrant 2. |
| 13. Cx = 5 + (-3) = 2 as shown on
page 83. Perform a similar addition to get Cy. (a) Write vector-C in component form using the i and j unit vectors. (b) Draw all vectors on the same axis; make sure their tails coincide with the origin. (c) Find the magnitude of vector-C using the Pythagorean Theorem. What quadrant does the vector point in? Find the related angle. |
| 14. Dx = 5 - (-3) = 8 as shown on
page 84. Perform a similar addition to get Dy. a) Write vector-D in component form using the i and j unit vectors. (b) Draw all vectors on the same axis; make sure their tails coincide with the origin. (c) Find the magnitude of vector-D using the Pythagorean Theorem. What quadrant does the vector point in? Find the related angle. |
| error log #1--- Note the correction to problem 18: the vector in the original axes system should read (-Bcos30, Bsin30). ie. note the minus sign on the x-component. |
| more hints later ; check back soon ! |
| EXPLANATION OF GRAPHING HANDOUTS |
Note this EXPLANATION makes more sense for section 02, which dealt with all this last WED with the handouts. Section 01's experiment is in the future. I can provide the lab handouts during the next lecture. Either way, this message is useful. There are two logical choices based upon the handout on graphing by hand. Below applies to the fresh graph paper I gave you. 1) For the vertical axis ( for v in cm/s), 5 darkest major divisions (i.e. 50 small divisions ) represents an interval of 100 units (100 cm/s). Thus 1 small division represents an interval of 2 units (2 cm/s) . This scaling could work for your data with smart choices for where 100 cm/s is marked on the vertical axis. To capture most of the data points you can: (i) set the 100 cm/s mark to be ten small divisions from the bottom of the vertical axis, (ii) count 50 small divisions up (count 5 darkest major divisions up) to mark 200 cm/s, (iii ) then count count 50 more small divisions up (count 5 more darkest major divisions up) to mark 300 cm/s, (iv) and finally count 30 small divisions up ( count 3 more darkest major divisions up) to mark 360 cm/s. In this scenario, 360 cm/s will be marked at the very top of the vertical axis. Please make appropriate adjustments for marking the first velocity value on the vertical axis to make sure the extrapolated "best fit" line goes through the vertical axis at t = 0. You want to be able to see the initial velocity ( at t = 0.) In this scenario, you could choose 5 small divisions to represent a time interval of 1/60 sec on the horizontal axis. 2) This next choice has poorer resolution. For the vertical axis ( for v in cm/s), 5 alternating darkest and less dark major divisions (i.e. 25 small divisions ) represents an interval of 100 units 100 cm/s). Thus 1 small division represents an interval of 4 units (4 cm/s) . This scaling would work for your data, without the worry that not all of the data points will fit on the graph paper, but with a loss of resolution in the graphing process. To capture most of the data points you can: (i) set the 100 cm/s mark to be 25 small divisions from the bottom of the vertical axis, (ii) count 25 small divisions up (count 5 alternating darkest and less dark major divisions up ) to mark 200 cm/s, (iii ) then count 25 more small divisions up (count 5 alternating darkest and less dark major divisions up) to mark 300 cm/s, (iv) and finally count 25 more small divisions up (count 5 alternating darkest and less dark major divisions up) to mark 400 cm/s, etc The extrapolated "best fit" line is guaranteed to go through the vertical axis at t = 0 such than you can see the initial velocity ( at t = 0.) In this scenario, you could also choose 5 small divisions to represent a time interval of 1/60 sec on the horizontal axis.. SUMMARY FROM THE HANDOUT Yo, what do these two above scenarios have in common in conjunction with the provided graph paper that works well with the decimal system? Read the handout again to find out: The bottom line is ( see page 59 top and Fig. 5.1) that the number of units between adjacent major divisions must be 1x10^N, 2x10^N or 5x10^N. # In scenario (1) above, on the vertical axis we had 1x10^N with N = 2, which equals 100 units between two adjacent darkest major divisions (10 small divisions apart). # In scenario (2) above, on the vertical axis we also had 1x10^N with N = 2, which equals 100 units between alternating darkest and less dark adjacent major divisions (5 small divisions apart.) # In both scenarios, on the horizontal axis, we had 5x10^N with N = 0, which equals the number of units between adjacent darkest and less dark major divisions (separated by 5 small divisions.). Note: One unit = 1/60 seconds. 5 small divisions = 1/60 second. Finally, in Figure 5.1, also explained on page 59 top, on the vertical axis, 1 darkest major division (i.e. 10 small divisions ) represents an interval of 20 units. That's 2x10^N with N = 1. Thus 1 small division represents an interval of 2 units. On the horizontal axis, 1 darkest major division (10 small divisions) represents 5 units. That's 5x10^N with N = 0. Note that we consider the time values in all cases to be exact. Remember that all of this discussion assumes the decimal based graph paper provided free of charge in the lab sessions. |