homework 03-solutions

# Answer in kg m s correct answer 6 8639 kg m s

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Unformatted text preview: n: We use the same procedure as in part 1 again. We already know the length of ~ D, so p we just need the length of ~ E : p j~ E j = p = ( pC) 2 + ( pC) 2 + ( pC) 2 x y z 4 q q ( pE ) 2 + ( pE ) 2 + ( pE ) 2 x y z (8 :97) 2 + ( p = 84:1858 = 9 :17528 : 1:93) 2 + (0) 2 So the dierence is given by j~ E j j ~ Dj = 6 :8639 kg m =s: p p So the dierence is given by j~ Cj j ~ Bj = p p 0:465923 kg m =s: Now nd ~ CD, the change between locations p C and D . Answer in kg m =s. Correct answer: Explanation: 1:36875 kg m =s. Between which two locations is the magnitude of the change in momentum greatest? 1. Between points B and C 2. Between points D and E correct 3. Between points C and D Explanation: cai (atc667) { homework 03 { turner { (57345) 5 Speed is just the magnitude of the velocity, so no vectors are involved. We just need to carry out the multiplication An electron travels at speed j~ = 0 :998c; vj where 3 108 m =s m/s is the speed of light. The electron travels in the direction given by the unit vector v = h0:655; 0:492; 0:573i : ^ The mass of an electron is 9 What is the value of =s 10 kg. j~ vj c ? 108 m =s) What is the magnitude of the electron’s momentum? Answer in kg m =s: Correct answer: 4 :26267 1 1 −31 j~ = 0 :998 c = 0 :998(3 vj = 2 :994 108 m =s : 10−21 kg m =s. Explanation: Relativistically, the magnitude of momentum is given by 2 You can simplify the calculation if you notice 2 j~ vj = (0 :998) 2. Also, remember that that c is a unitless quantity. j~ = m j~ : pj vj We know as well as m and j~ , so we have vj everything we need. We obtain Correct answer: 15 :8193. Explanation: This is just a plug and chug problem. You can carry out the calculation with the more complicated expression or you can take the hint into account and simplify things to nd that =s =s j~ vj c 1 ~ = hpx; py; pzi : p 2 0:998 c c = 15 :8193 : 1 2 What is the speed of the electron? Answer in m/s. Correct answer: 2 :994 Explanation: 108 m =s) The full vector momentum of the electron would be of the form 1 1 j~ = m j~ pj vj = (15 :8193)(9 10−31 kg)(2 :994 = 4 :26267 10−21 kg m =s : 108 m =s. Find px in kg m =s. Remember that any vector can be \factored" into its magnitude tim...
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