物理 高中 4年以上以前

請問A是1.1cm嗎？

的三頜萬入/赴健 )2. 第五代行動逼訊-C5G-~Generation Mobile_ Networks Allianc) 的時代來品 將採用8oHz 及 60G卻 毫米波通訊,比如目前 4G 使用 700M 900MHz、1800MHZ ~ 2600MHz 等低頻段,雖然電波繞射能力比較高 吳在低頻上頻譜資源卻相當有限,在高頻的毫米波大多是軍用戰耳機 達或測臺照相等少數裝置,頻譜寬度更高,而且更容易找到連續頻譜 太 _使空白頻譜非常容易取得,下詢敘述哪些正確? (應選2項) | (一四的全 計語時 11 mm “8頻率越大者 , 只傳播速度越大_(t)疲長越大者,其傳播速度越大 “DB畫能在地球 重播”可以在太空中使用

物理 高中 約5年以前

求解(・・;

讓9 在平面上有一質點質量為2 上次S 公反7秘的速度向西偏北 53"作 品琳()註0秒時,質點相對於 0點角 謹慷芷 公斤,公中2/秒。(2)t =2秒時,質一 論點角動量量值為_ 公斤2 AR 相對O點而言 , 若忽略空握力, ,則有 還人Sai 和杰球所受的力矩的敘述,則 (1)斷上的張力一影響小球 极角動量(填會或不會,並解釋) (2)小球角動量在5點時 莽在P點時為一_(填大或小或相等,並解釋) (3)小球所受的重力力矩,在 2點時比在Q點時為-__(填大或小或相等,並解釋) (4)小球角動量隨時間 的改變率,在5點時比在Q點時為一-(填大或小或相等,並解釋)。 (Homework)一質點以 O 為圓心在一水平面上作等束 圓周運動,其速率為v,如圖所示。將圓周均分為8 還2ATB~C、D、E、T 皆在圓周等分點上,如 果以f點為參考點測量質點的角動量,則該質點角 動量時間變1 率的量值在圖中哪一處最大? (Homework) 某質點以等速度沿 人 ,如 圖所示,當其通崗A點時,對0點的 一和 品 RO ,對0 上

物理 高中 5年以上以前

18題，感謝

10. [2D and 3D motion] Show that the potential energy U(r) ofFa particle of nass jat aa distance r(> 員 from a planet of Inass 4 and radins 戶話 11. [The cross product] Caleulate the cross product A x B, assuming that A and B both lie in the x-y plane and have the respective nonzero components 4,, 4, and 妖,, 且, 12. [Angular momentum] Show that 主r, the instantaneous position ofa particle of mass mu with respect to a certain origin O, is parallel to its acceleration dv/吧, then the time Tate of change of the angular Inoimentum L with respect to the given origin vanishes 13. [Theorem 了 Show that the torque-angular momentum formnla _箇 7二 is also valid for a two-particle system 放 the origin lies at the center of mass 14. [Theorem IIH] Two particles of respective Inass ml and 2 are connected to the ends of amassless rod and Inove in the uniform gravitational field g ofthe earth. (a) What is the acceleration of their center of nass Telative to a Newtonian origin O? (b) Show that the angular Inomentum of the two particles about their center of nass 生 aconstant of the motion. 15. [Moments of inertia] Calculate the moment of inertia ofathin, uniform rod of mass m and length / about an axis perpendicular to the rod and at a distance q from one end. 16. [Rotation about a fixed axis] Consider the rotating cylinder in Figure, and suppose that A7 sg, Fo 三 0.6 Nt, and @ 二 0.2m, Calculate (a) The torque 7 acting on the cylinder (b) Ti ngular aceeleration q of the cylinder 17. [Work and kinet: instant Totat eenergy] A 40-kg homogeneous sphere of radius 10 cm is at acertain about ashaft through its center at 600 rpm. Assuining that a constant fric itude ets so that the sphere comes to rest in 10 seconds, Calculate th tional torque ofthis torque. 18. [The physical pendl end and allowed to oscillate freely in a horizontal plane (see Figure) m] A uniform Tod of Inass ru and length / is suspended at one (a) What is the period of this physic lpendulum for small amplitudes? (b) Ithe velocity u0 of the mass ce Hulum is initially released at rest in a horizontal position。what is the er at a subsequent instant when the Tod is vertical? (ec) Calculate the vertical and the horizontal components of the force on the rod at the point of suspensic 19 and rotations] Analyze the motion of a homogeneous sphere of mass 和7 and Tadius dq, which rolls without slipping down a fixed inclined plane of angle # 20. of angular momentum] A Inan has ainoment of inertia 五 about the = axis. He is originally at Test and standing on asinall platform which can turn freely. Ifhe is handed a wheel which is rotating at and has anoinent of inertia 了about its spinning axis, determine his angular velocity 放 (a) he holds the wheel upright, (b) turns the wheel out 9 二 90?, and (c) turns the wheel downward, 9 二 180?. Neglect the effect of holding the wheel a distance d away from the z axis