PHY131: Tutorial Problems 1
Tutoriaal Probleme 1
2012
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Week: 20 February 2012 / 20 Februarie 2012
1. How many significant figures do each of the following numbers have: (a)
214, (b) 81.60, (c) 7.03, (d) 0.03, (e) 0.0086, (f) 3326, and (g) 8700?
2. Add (9.2 × 103 s) + (8.3 × 104 s) + (0.008 × 106 s).
3. A light-year is the distance light travels in one year (at speed = 2.998 ×
108 m/s). (a) How many meters are there in 1.00 light-year? (b) An
astronomical unit (AU) is the average distance from the Sun to Earth,
1.50 × 108 km. How many AU are there in 1.00 light-year? (c) What is
the speed of light in AU/h? [Answers: (a) 9.46×1015 m, (b) 6.31×104 AU,
(c) 7.2 AU/h]
4. A typical atom has a diameter of about 1.0 × 10−10 m. Approximately
how many atoms are there along a 1.0 cm line? [Answer: 1.0 × 108 atoms]
5. If Vx = 6.80 units and Vy = −7.40 units, determine the magnitude and
~ . [Answers: 10.0 units, −47◦ w.r.t. positive x]
direction of V
~ can be written (Vx , Vy , Vz ). What are the
6. The components of a vector V
components and length of a vector which is the sum of the two vectors,
V~1 and V~2 , whose components are (8.0, −3.7, 0.0) and (3.9, −8.1, −4.4)?
[Answers: (11.9,-11.8,-4.4), 17.3 units]
~ is a vector 14.3 units in magnitude and points at an angle of 34.8◦ above
7. V
the negative x axis. (a) Sketch this vector. (b) Find Vx and Vy . (c) Use
~ . [Answers:
Vx and Vy to obtain (again) the magnitude and direction of V
(b) Vx = −11.7 units, Vy = 8.16 units]
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The next two problems refer to the figure above:
~ − C.
~ [Answer: |A
~ − C|
~ = 64.6 units, θ = 53.1◦ ]
8. Determine the vector A
~ − A.
~ (b) Determine A
~−B
~ without using your answer
9. (a) Determine B
~ − A|
~ = 53.7 units,
in (a). Then compare the results. [Answer: (a) |B
◦
θ = 1.4 above the x-axis]
Problems from Zinke-Allmang: P-2.3, P-1.2, P-1.3
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