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# hw9 - wilson(kw22588 – HW9 – Mackie –(20224 1 This...

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Unformatted text preview: wilson (kw22588) – HW9 – Mackie – (20224) 1 This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 3) 10.0 points The magnetic field over a certain range is given by vector B = B x ˆ ı + B y ˆ , where B x = 8 T and B y = 5 T. An electron moves into the field with a velocity vectorv = v x ˆ ı + v y ˆ + v z ˆ k , where v x = 4 m / s, v y = 8 m / s and v z = 4 m / s. The charge on the electron is − 1 . 602 × 10 − 19 C. What is the ˆ ı component of the force ex- erted on the electron by the magnetic field? Correct answer: 3 . 204 × 10 − 18 N. Explanation: Let : v x = 4 m / s , v y = 8 m / s , v z = 4 m / s , q = − 1 . 602 × 10 − 19 C , B x = 8 T , and B y = 5 T . The force exerted on the electron by the mag- netic field is given by vector F = qvectorv × vector B = q vextendsingle vextendsingle vextendsingle vextendsingle vextendsingle vextendsingle ˆ ı ˆ ˆ k v x v y v z B x B y vextendsingle vextendsingle vextendsingle vextendsingle vextendsingle vextendsingle = q [ − v z B y ˆ ı + v z B x ˆ + ( v x B y − v y B x ) ˆ k ] = ( − 1 . 602 × 10 − 19 C) {− (4 m / s) (5 T)ˆ ı + (4 m / s) (8 T)ˆ + [(4 m / s) (5 T) − (8 m / s) (8 T)] ˆ k } = (3 . 204 × 10 − 18 N)ˆ ı + ( − 5 . 1264 × 10 − 18 N)ˆ + (7 . 0488 × 10 − 18 N) ˆ k 002 (part 2 of 3) 10.0 points What is the ˆ component of the force? Correct answer: − 5 . 1264 × 10 − 18 N. Explanation: See the above part. 003 (part 3 of 3) 10.0 points What is the ˆ k component of the force? Correct answer: 7 . 0488 × 10 − 18 N. Explanation: See the above part. 004 (part 1 of 2) 10.0 points An electron in an electron beam experiences a downward force of 3 . × 10 − 14 N while trav- eling in a magnetic field of 4 . 1 × 10 − 2 T west. The charge on a proton is 1.60 × 10 − 19 . a) What is the magnitude of the velocity? Correct answer: 4 . 57317 × 10 6 m / s. Explanation: Let : F m = 3 . × 10 − 14 N , B = 4 . 1 × 10 − 2 T , and q e = 1 . 60 × 10 − 19 C . The magnetic force is F m = q v B v = F m q B = 3 × 10 − 14 N (1 . 6 × 10 − 19 C) (0 . 041 T) = 4 . 57317 × 10 6 m / s 005 (part 2 of 2) 10.0 points b) What is its direction? 1. East 2. None of these 3. West 4. North correct wilson (kw22588) – HW9 – Mackie – (20224) 2 5. South Explanation: Apply right-hand rule (for a negative charge); force directed into the palm of the hand, fingers in the direction of the field, thumb in the direction of the velocity....
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hw9 - wilson(kw22588 – HW9 – Mackie –(20224 1 This...

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