q8_c27_sol

# q8_c27_sol - 3 At t=0 the value of a in cm is a 0.500 b...

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Solutions to Quiz 8 Phys. 2306 F09 You may use your text book, notes, and a calculator. A particle with negative charge - q and mass m = 2 . 00 × 10 - 15 kg is traveling at t = 0 with ( v x , v y , v z ) = 1 . 00 × 10 6 ( - 3 , 4 , 5) m/s , at position ( x, y, z ) = ( a, 0 , 0) m. At all times it travels in a region of constant magnetic field, ( B x , B y , B z ) = (0 , 0 , - 0 . 100) T. 1) If at t=0, the magnitude of the force on the particle is 1.00 N, what is q in 10 - 6 C? a) 0.500 b) 1.00 c) 2.00 d) 5.00 e) none of these F = q v × B , = q (1 . 00 × 10 6 )(0 . 100)( - 3 i + 4 j + 5 k ) × - k , = q (1 . 00 × 10 5 )( - 3 j - 4 i ) , F = q (5 . 00 × 10 5 ) = 1 . 00 , q = 2 . 00 × 10 - 6 C. ( c ) 2) At some arbitrary later time the magnitude of the force a) increases b) decreases c) is the same d) could increase or decrease e) insuffi- cient information F · v = 0 , thus | v | is unchanged and since F B, F z = 0 , v z is constant. So | F | is constant, (c)

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Unformatted text preview: 3) At t=0 the value of a in cm is a) 0.500 b) 1.00 c) 2.00 d) 5.00 e) none of these Particle moves in a circle with radius a in the xy plane so, 1 F = m ( v 2 x + v 2 y ) /a, a = 100[2 × 10-15 (3 2 + 4 2 ) × 10 12 / 1 . 00] cm = 5 cm 4) What is the next time in 10-8 s that ( x, y ) = ( a, 0) ? a) 6.28 b) 3.14 c) 1.57 d) 0.785 e) none of these The time is the period for 1 revolution, so, t = 2 πa/ q v 2 x + v 2 y , = 2 π (0 . 05) / 5 × 10 6 s = 6 . 28 × 10-8 s, ( a ) . 5) What is z in cm at this time? a) 62.8 b) 31.4 c) 15.7 d) 7.85 e) 0 z = z (0) + v z t, = 0 + 100[(5 . 00 × 10 6 )(6 . 28 × 10-8 )] cm, = 31 . 4 cm, ( b ) 2...
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