hw2_sol_sp10

hw2_sol_sp10 - Physics 101 Classical Physics Spring 2010...

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Unformatted text preview: Physics 101 Classical Physics Spring 2010 Homework 2 Solutions DUE IN CLASS ON JANUARY 28 1. A ball is released from rest and falls a distance h under the influence of gravity. What is its average speed during the fall? (a) r 1 2 gh , (b) 1 2 gh , (c) 2 gh , (d) gh , (e) 2 gh 0 = h- 1 2 gt 2 t = s 2 h g x t = h p 2 h/g = r 1 2 gh 2. A vector ~ A = 6 i is added to a vector B =- 8 j . Their sum ~ C = ~ A + ~ B is: (a) 14 k , (b)- 2 k , (c) 6 i + 8 j , (d)6 i- 8 j , (e) -2 3. The smallest the magnitude of the sum of two vectors can be occurs when: (a) The vectors are identical, (b) The vectors point in the same direction, (c) The vectors are perpendicular to each other, (d) There is an angle of 45 between them (e) They point in opposite directions 4. A vector of magnitude 10 is added to another of magnitude 15. The magnitude of this sum can be: (a) 0, (b) 35, (c) 3, (d) 12 , (e) 50 The magnitude must be greater than 5 (vectors point in opposite directions) and less than 25 (vectors point in same direction). 5. Which of the following is a scalar quanity? (a) velocity, (b) displacement, (c) mass , (d) acceleration, (e) none of these 1 6. A vector A has a magnitude of 5.0 and has an angle of 60 with respect to the horizontal positive x-axis, measuring counter-clockwise from that axis. Vector B has a magnitude of 10.0 and makes an angle of 60 with the vertical positive y-axis, measuring clockwise from that axis. What vector represents the sum of the two vectors, using the notation where i is the unit vector in the postive x direction, and j is the unit vector in the positive y direction? Referencing both angles from the positive x-axis and adding the components separately, ~ A = 5cos(60 ) i + 5sin(60 ) j = 5 2 i + 5 3 2 j ~ B = 10cos(30 ) i + 10sin(30 ) j = 5 3 i + 5 j ~ A + ~ B = ( 5 2 + 5 3 ) i + 5 3 2 + 5 j = 5 2 (1 + 2 3) i + 5 2 (2 + 3) j 7. Use the following figure and information for the next 4 questions. As shown in the figure, a vector A makes an angle with the y-axis of a rotated...
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hw2_sol_sp10 - Physics 101 Classical Physics Spring 2010...

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