相關(guān)習(xí)題
 0  122286  122294  122300  122304  122310  122312  122316  122322  122324  122330  122336  122340  122342  122346  122352  122354  122360  122364  122366  122370  122372  122376  122378  122380  122381  122382  122384  122385  122386  122388  122390  122394  122396  122400  122402  122406  122412  122414  122420  122424  122426  122430  122436  122442  122444  122450  122454  122456  122462  122466  122472  122480  176998 

科目: 來源: 題型:


如圖所示,水平傳送帶長L=2.45m,以速度V1=4m/s順時(shí)針運(yùn)動,傾斜的傳送帶足夠長,與水平面的夾角θ=37°,以速度V2=2m/s                                                                                        順時(shí)針運(yùn)動,兩傳送帶連接處平滑過渡,把一物塊無初速從左端放上傳送帶,物塊與傳送帶間的動摩擦因數(shù)μ=0.5,求:                                    

(1)物塊到水平傳送帶右端的速度.                                                                              

(2)從物塊開始滑上傾斜傳送帶開始計(jì)時(shí),2S內(nèi)物塊距底端的最大距離.                        

                                                                              

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


某同學(xué)用伏安法測一節(jié)干電池的電動勢E和內(nèi)電阻r,所給的其它器材有:                         

A.電壓表V:0~3~15V                                                                                                

B.電流表A:0~0.6~3A                                                                                                

C.變阻器R1:(20Ω,1A)                                                                                            

D.變阻器R2:(1000Ω,0.1A)                                                                                      

E.電鍵S和導(dǎo)線若干                                                                                                      

                                      

(1)實(shí)驗(yàn)中電壓表應(yīng)選用的量程為                                                              (填0~3V或0~15V);電流表應(yīng)選用的量程為                                                                                                           填0~0.6A或0~3A);變阻器應(yīng)選用        ;

(2)根據(jù)實(shí)驗(yàn)要求連接實(shí)物電路圖(圖1);                                                                  

(3)實(shí)驗(yàn)測得的6組數(shù)據(jù)已在U﹣I圖2中標(biāo)出,如圖2所示.請你根據(jù)數(shù)據(jù)點(diǎn)位置完成U﹣I圖線,并由圖線求出該電池的電動勢E=                                                                                                  V,電阻r= Ω.           

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


(1)某同學(xué)探究恒力做功和物體動能變化間的關(guān)系,方案如圖1所示.他想用鉤碼的重力表示小車受到的合外力,為減小這種做法帶來的誤差,實(shí)驗(yàn)中要采取的兩項(xiàng)措施是:                                                       

a                                                                                                                   ;               

b                                                                                                          .                      

(2)如圖2所示是某次實(shí)驗(yàn)中得到的一條紙帶,其中A、B、C、D、E、F是計(jì)數(shù)點(diǎn),相鄰計(jì)數(shù)點(diǎn)間的時(shí)間間隔為T.距離如圖.則打B點(diǎn)時(shí)的速度為vB=                                                                         .            

                                     

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


如圖所示,相距為d的兩條水平虛線L1、L2之間是方向水平向里的勻強(qiáng)磁場,磁感應(yīng)強(qiáng)度為B,質(zhì)量為m、電阻為R的正方形線圈abcd邊長為L(L<d),將線圈在磁場上方高h(yuǎn)處由靜止釋放,cd邊剛進(jìn)入磁場時(shí)速度為v0,cd邊剛離開磁場時(shí)速度也為v0,則線圈穿越磁場的過程中(從cd邊剛?cè)氪艌鲆恢钡絘b邊剛離開磁場)(   )                              

                                                                                         

    A.  感應(yīng)電流做功為mgl

    B.  感應(yīng)電流做功為2mgd

    C.  線圈的最小速度可能為

    D.  線圈的最小速度一定為

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


在光滑絕緣水平面上,一輕繩拉著一個帶電小球繞豎直方向的軸O在勻強(qiáng)磁場中做順時(shí)針方向的水平勻速圓周運(yùn)動,磁場方向豎直向下,其俯視圖如圖所示.若小球運(yùn)動到A點(diǎn)時(shí),繩子突然斷開,關(guān)于小球在繩斷開后可能的運(yùn)動情況,以下說法正確的是(                                                                                )                               

                                                                                                                     

    A.  小球做順時(shí)針方向的勻速圓周運(yùn)動,周期變小

    B.  小球做順時(shí)針方向的勻速圓周運(yùn)動,周期不變

    C.  小球仍做逆時(shí)針方向的勻速圓周運(yùn)動,速度增大

    D.  小球仍做逆時(shí)針方向的勻速圓周運(yùn)動,但半徑減小

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


如圖所示,光滑絕緣細(xì)桿AB,水平放置于被固定的帶負(fù)電荷的小球的正上方,小球的電荷量為Q,可視為點(diǎn)電荷.a(chǎn)、b是水平細(xì)桿上的兩點(diǎn),且在以帶負(fù)電小球?yàn)閳A心的同一豎直圓周上.一個質(zhì)量為m、電荷量為q的帶正電的小圓環(huán)(可視為質(zhì)點(diǎn))套在細(xì)桿上,由a點(diǎn)靜止釋放,在小圓環(huán)由a點(diǎn)運(yùn)動到b點(diǎn)的過程中,下列說法中正確的是 (    )                        

                                                                                                    

    A.  小圓環(huán)所受庫侖力的大小先增大后減小

    B.  小圓環(huán)的加速度先增大后減小

    C.  小圓環(huán)的動能先增大后減小

    D.  小圓環(huán)與負(fù)電荷組成的系統(tǒng)電勢能先增大后減小

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


如圖所示,在AB間接入正弦交流電U1=220V,通過理想變壓器和二極管D1、D2給阻值R=20Ω的純電阻負(fù)載供電,已知D1、D2為相同的理想二極管,正向電阻為0,反向電阻無窮大,變壓器原線圈n1=110匝,副線圈n2=20匝,Q為副線圈正中央抽頭,為保證安全,二極管的反向耐壓值至少為U0,設(shè)電阻R上消耗的熱功率為P,則有(       )                               

                                                                                      

    A. U0=40V,P=80W      B. U0=40V,P=80W

    C. U0=40V,P=20W      D.       U0=40V,P=20W

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


如圖所示,在同一軌道平面上的三個人造地球衛(wèi)星A、B、C在某一時(shí)刻恰好在同一直線上,下列說法正確的有(   )                                                                                                                                   

                                                                                                    

    A.  根據(jù)v=,可知vA<vB<vC

    B.  根據(jù)萬有引力定律,F(xiàn)A>FB>FC

    C.  向心加速度aA>aB>aC

    D.  衛(wèi)星中的物體對地面的壓力等于地球?qū)ξ矬w的萬有引力

                                                                                                                                       

查看答案和解析>>

科目: 來源: 題型:


一噴泉射出的水上升的高度為h,出口的橫截面積為s,已知水的密度為ρ,由空中水的質(zhì)量為( )

  A. ρsh B. 2ρsh C.3ρsh D.4ρsh

查看答案和解析>>

科目: 來源: 題型:


如圖所示,圓柱體的A點(diǎn)放有一質(zhì)量為M的小物體P,使圓柱體緩慢勻速轉(zhuǎn)動,帶動P從A點(diǎn)轉(zhuǎn)到A′點(diǎn),在這個過程中P始終與圓柱體保持相對靜止.那么P所受靜摩擦力f的大小隨時(shí)間t的變化規(guī)律是( )

A. B. C. D.

查看答案和解析>>

同步練習(xí)冊答案