一根輕彈簧原長為X₀,當(dāng)掛一質(zhì)量為m₁的砝碼靜止時(shí),其總長為X₁,求:

(1)  該彈簧的勁度系數(shù)K為多少?

(2)  當(dāng)改掛質(zhì)量為m₂的砝碼靜止時(shí),其總長為多少?

(1)用螺旋測(cè)微器測(cè)量一根金屬絲的直徑，如圖所示的讀數(shù)是   ▲    mm．

（2）有同學(xué)利用如右圖的裝置來驗(yàn)證力的平行四邊形定則：在豎直木板上鋪有白紙，固定兩個(gè)光滑的滑輪A和B，將繩子打一個(gè)結(jié)點(diǎn)O，每個(gè)鉤碼的質(zhì)量相等，當(dāng)系統(tǒng)達(dá)到平衡時(shí)，根據(jù)鉤碼個(gè)數(shù)讀出三根繩子OA、OB、OC的拉力T_OA、T_OB和T_OC，回答下列問題：

①改變鉤碼個(gè)數(shù)，實(shí)驗(yàn)?zāi)芡瓿傻氖牵?nbsp;       ）

A．鉤碼的個(gè)數(shù)N₁=N₂=2，N₃=4  

B．鉤碼的個(gè)數(shù)N₁=N₃=3，N₂=4 

C．鉤碼的個(gè)數(shù)N₁=N₂=N₃=4

D．鉤碼的個(gè)數(shù)N₁=3，N₂=4，N₃=5

②在拆下鉤碼和繩子前，應(yīng)記錄下：

　　　▲　       ；　　　　▲　       ��；　　　　▲　      

如圖所示, 傾角為θ的絕緣斜面固定在水平面上,  當(dāng)質(zhì)量為m、帶電荷量為+q的滑塊沿斜面勻速下滑時(shí),在此空間突然加上豎直方向的勻強(qiáng)電場(chǎng),已知滑塊受到的電場(chǎng)力小于滑塊的重力．則（   ）

  A．加上豎直向上的電場(chǎng)后,滑塊將減速下滑?

  B．加上豎直向下的電場(chǎng)后,滑塊仍勻速下滑

    C．加上豎直向上的電場(chǎng)后,滑塊仍勻速下滑?

D．加上豎直向下的電場(chǎng)后,滑塊將加速下滑?

如圖一所示，在一水平放置的平行金屬板電容器間加上圖二所示的交變電壓，在平行板電容器的右面距離為L處是一豎直放置的屏�，F(xiàn)有質(zhì)量為m、帶電量為q的粒子，連續(xù)不斷地從平行板電容器的正中央以水平速度v₀射入。已知平行板電容器板長為L，兩板間距離為d，兩板間所加電壓的周期為T，電壓大小為u₀，不計(jì)重力。求：

(1)若，求帶電粒子打在屏上離O點(diǎn)的最大距離。(粒子與板不會(huì)發(fā)生接觸)

(2)若，求帶電粒子打在屏上離O點(diǎn)的最大距離。(粒子與板不會(huì)發(fā)生接觸)

下圖是某同學(xué)連接的實(shí)驗(yàn)實(shí)物圖，閉合開關(guān)S后，發(fā)現(xiàn)A、B燈都不亮，他采用下列兩種方法檢查故障：（每節(jié)干電池電動(dòng)勢(shì)約為1.5V）

(1)用多用電表的直流電壓檔進(jìn)行檢查：

①那么選擇開關(guān)應(yīng)置于下列量程的_______________檔．(用字母序號(hào)表示)

A. 2.5V     B. 10V      C. 50V      D. 250V

②該同學(xué)測(cè)試結(jié)果如下表所示，根據(jù)測(cè)試結(jié)果，可以判定故障是_______________．(假設(shè)只有下列中的某一項(xiàng)有故障)

A. 燈L₁斷路         B. 燈L₂短路

C. c、d段斷路       D. d、f段斷路

(2)用歐姆檔檢查：

①測(cè)試前，應(yīng)將開關(guān)S__________(填“斷開”或“閉合”)

②測(cè)量結(jié)果如右表所示，由此可以斷定故障是__________．

A. 燈L₁斷路             B. 燈L₂斷路

C. 燈L₁、L₂都斷路       D. d、e間導(dǎo)線斷路

一快艇要從岸邊某處到達(dá)河中離岸100 m遠(yuǎn)的浮標(biāo)處，已知快艇在靜水中的速度圖象如圖甲所示，流水的速度圖象如圖乙所示，假設(shè)行駛中快艇在靜水中航行的分速度方向選定后就不再改變，則                                                                                           (　  )

A．快艇的運(yùn)動(dòng)軌跡可能是直線                      B．快艇的運(yùn)動(dòng)軌跡只可能是曲線

C．達(dá)到浮標(biāo)處通過的最小位移為100 m         D．最快達(dá)到浮標(biāo)處所用時(shí)間為20 s

一輛汽車在行駛中發(fā)生漏油，假如每隔l s漏下一滴，車在平直公路上行駛，一位同學(xué)根據(jù)漏在路面上的油滴分布，分析汽車的運(yùn)動(dòng)情況（已知車的運(yùn)動(dòng)方向）。下列說法中正確的是（   ）                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               A．當(dāng)沿運(yùn)動(dòng)方向油滴間距逐漸增大時(shí)，車一定在做減速直線運(yùn)動(dòng)

B．當(dāng)沿運(yùn)動(dòng)方向油滴始終均勻分布時(shí)， 車可能做勻速直線運(yùn)動(dòng)

C．當(dāng)沿運(yùn)動(dòng)方向油滴間距逐漸增大時(shí)，車一定在做勻加速直線運(yùn)動(dòng)

D．當(dāng)沿運(yùn)動(dòng)方向油滴間距逐漸增大時(shí)，車的加速度一定也增大