Question

高中物理第五题求解

Answer 1

答案：C
<span style="font-size:9.0pt;mso-bidi-font-size:10.5pt;
font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman";mso-bidi-font-family:Tahoma;color:#333333;mso-font-kerning:
1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:
AR-SA;mso-bidi-font-weight:bold">解析：因为洛伦兹力<span lang="EN-US" style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:"Times New Roman";
mso-fareast-font-family:宋体;mso-bidi-font-family:Tahoma;color:#333333;
mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;
mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">F<span style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";mso-bidi-font-family:
Tahoma;color:#333333;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:
ZH-CN;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">与重力<span lang="EN-US" style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:"Times New Roman";
mso-fareast-font-family:宋体;mso-bidi-font-family:Tahoma;color:#333333;
mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;
mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">mg<span style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";mso-bidi-font-family:
Tahoma;color:#333333;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:
ZH-CN;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">的合力与速度<span lang="EN-US" style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:"Times New Roman";
mso-fareast-font-family:宋体;mso-bidi-font-family:Tahoma;color:#333333;
mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;
mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">v<span style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";mso-bidi-font-family:
Tahoma;color:#333333;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:
ZH-CN;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">反向，所以质点速度会减小，速度减小，洛伦兹力<span lang="EN-US" style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:"Times New Roman";
mso-fareast-font-family:宋体;mso-bidi-font-family:Tahoma;color:#333333;
mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;
mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">F<span style="font-size:9.0pt;mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";mso-bidi-font-family:
Tahoma;color:#333333;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:
ZH-CN;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">也一定减小。所以减小后的洛伦兹力与重力的合力方向一定与速度不在一条直线上，所以质点不会做直线运动，故A错；又因为质点所受合力不恒定（大小、方向都在变），所以不会做匀减速运动，故B错；又因为合力的大小在变化，所以质点不可能做匀速圆周运动，故D错。

追问

？

Answer 2

C

追答

洛伦磁力大小方向都在变

合力方向也不与V垂直，故不可能做圆周运动！

嗯