# 美国物理竞赛F=ma真题开放中！

• 2022 年 1 月 21 日 – F=ma 注册截止日期
• 2022 年 2 月 9 日 - F=ma 考试 A
• 2022 年 2 月 15 日 – F=ma 考试 B
• 2022 年 6 月上旬 -马里兰大学美国物理队训练营

F=ma试题的难度在AP Physics C Mechanics之上，但并不需要微积分基础。同学们可以在学习AP Physics C Mechanics的基础上，通过做往年的题目进行能力提升和查漏补缺。

1.A point mass m is glued inside a massless hollow rod of length I at an unknown location. When the rod is pivoted at one end, the period of small oscillations is T. When the rod is pivoted at the other end, the period of small oscillations is 27. How far is the mass from the center?

(A)L/8

(B)L/6

(C)L/4

(D)3L/10

(E)2L/5

2.A lballerina with moment of inertia I is quickly twirling with angular velocity e. In her hand she has a pen of mass m at a radius R from her axis of rotation. The ballerina releases the pen. Afterward, what happens to the vertical component of the angular momentum of the system consisting of the ballerina and the pen? You may ignore all friction, but not gravity or normal forces.

(A) It decreases until the pen hits the floor.

(B) It increases until the pen hits the floor.

(C) It always stays the same.

(D) It initially stays the same, but decreases when the pen hits the floor.(E) It initially stays the same, but increases when the pen hits the floor.

3. During this process, the block has been raised by approximately a height

(A)0.15L

(B)0.23L

(C)0.31L

(D)0.37L(E)0.40L