Answers for Practice Test #1

• [1] three step process to see if the unknown object attracts neutral, positive and netagive. Look at your notes (or student workbook from first Tuesday's lecture)
• [2] F3on1 = (-10.2i + 5.1j) N
• [3] 4>2>1=3>6>5 (we did one very similar to this in class)
• [4] (a) positive (charge in a field experiences a force, and force causes deflection upward)
  (b) 1 = negative, 4 = positive, 2 = neutral
  (c) 4 has more charge (stronger force)
• [5] vf = 3.372 x 10⁶m/s
• [6] Q = 4.85 x 10^-9C
• [7] if you don't know this you haven't been paying attention during the last three classes.
• [8] (a) E = 0 (do you know why?)
  (b) +2nC at r=a to balance point charge, +6nC total so +4nC at r=b, which means that eta = 3.54 x 10^-7C/m²
  (c) E = 22480 N/C