[問題] 兩題普物問題

[justalone101 (ㄚ挺)]

跟電學有關

1. A cube of edge "a"(邊長) carries a point charge q at each corner.

Show that the resultant electric force on any one of the charge

is given by:


             F = 0.262q^2 / εa^2




2. Two positive charges +Q are held fixed a distance d apart. A particle

of negative charge -q and mass "m" is placed midway between them, then is

given a small displacement perpendicular to the line joinging them and

relased.


Show that

the particle describes SHM of period = (εmπ^3d^3/qQ)^1/2


第二題我算的答案是 ("2"εmπ^3d^3/qQ)^1/2



麻煩各位幫忙解題一下 謝謝!!

--
※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 114.40.85.19
→ SmArTyau:第一題 從cube的最長的斜對角看 將它分成四層
→ SmArTyau:分別為1 3 3 1顆電子 然後計算2 3 4層對第1層的力
→ SmArTyau:第二題 F=-kx中的 k=4qQ/(πεd^3) T=2π[sqrt(m/k)]
→ justalone101:抱歉~第一題我還是不太懂耶 還有第二題的k為什麼是
→ justalone101: 4qQ/(πεd^3) 可以麻煩大大說明清楚一點嗎? 謝謝
→ ren1072:對角落的點電荷而言距離它a的電荷有三個//根號2*a的有三個
→ ren1072:根號3*a的有一個...