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sửa đổi
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Con lắc lò xo nằm ngang(5).
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Co $T=2\pi\sqrt{\frac{m}{k}}=0,5s$$<=>k=\frac{4\pi^2.m}{T}=50N/m$Vi con lac lo xo nam ngang nen luc dan hoi cuc dai la: $F_{max}=k(\Delta l+A)=kA=50.0,1=5N$
Co $T=2\pi\sqrt{\frac{m}{k}}=0,5s$$<=>k=\frac{4\pi^2.m}{T}=40N/m$Vi con lac lo xo nam ngang nen luc dan hoi cuc dai la: $F_{max}=k(\Delta l+A)=kA=40.0,1=4N$
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sửa đổi
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Con lắc lò xo nằm ngang(1).
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Dong nang bang 3 lan the nang thi $W_{d}=\frac{3}{4}W$ $<=>\frac{1}{2}m.v^2=\frac{3}{4}.\frac{1}{2}m.v^2_{max}$$<=>v=\pm \frac{\sqrt{3}}{2}v_{max}=\pm \frac{\sqrt{3}}{2}\frac{kA}{m}$
Dong nang bang 3 lan the nang thi $W_{d}=\frac{3}{4}W$ $<=>\frac{1}{2}m.v^2=\frac{3}{4}.\frac{1}{2}m.v^2_{max}$$<=>v=\pm \frac{\sqrt{3}}{2}v_{max}=\pm \frac{\sqrt{3}}{2}wA=\pm \frac{\sqrt{3}}{2}.A\sqrt{\frac{k}{m}}=\pm A\sqrt\frac{3k}{4m}$
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tính hệ số công suất
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Theo gia thiet thi khi noi tat tu dong dien trong hai truong hop vuong pha voi nhau nen: $\frac{R}{Z_{L}}=\frac{Z_{C}-Z_{L}}{R}=>Z_{C}-Z_{L}=\frac{R^2}{Z_{L}}$Khi noi tat tu ta cung co dien ap hieu dung giua 2 dau dien tro R tang 2 lan nen: $2\sqrt{R^2+Z^2_{L}}=\sqrt{R^2+(Z_{L}-Z_{C})^2}$ $<=>4R^2+4Z^2_{L}=R^2+\frac{R^4}{Z^2_{L}}$ $<=>R^4-3R^2.Z^2_{L}-4Z^4_{L}=0$ Day la pt dang cap dang co ban de dang suy ra $R=4Z_{L}$Khi do de dang tim dk he so cong suat cua doan mach luc sau $cos\varphi=\frac{R}{\sqrt{R^2+Z^2_{L}}}\frac{R}{\sqrt{R^2+\frac{R^2}{16}}}=\frac{4}{\sqrt{17}}$
Theo gia thiet thi khi noi tat tu dong dien trong hai truong hop vuong pha voi nhau nen: $\frac{R}{Z_{L}}=\frac{Z_{C}-Z_{L}}{R}=>Z_{C}-Z_{L}=\frac{R^2}{Z_{L}}$Khi noi tat tu ta cung co dien ap hieu dung giua 2 dau dien tro R tang 2 lan nen: $2\sqrt{R^2+Z^2_{L}}=\sqrt{R^2+(Z_{L}-Z_{C})^2}$ $<=>4R^2+4Z^2_{L}=R^2+\frac{R^4}{Z^2_{L}}$ $<=>R^4-3R^2.Z^2_{L}-4Z^4_{L}=0$ Day la pt dang cap dang co ban de dang suy ra $R=2Z_{L}$Khi do de dang tim dk he so cong suat cua doan mach luc sau $cos\varphi=\frac{R}{\sqrt{R^2+Z^2_{L}}}\frac{R}{\sqrt{R^2+\frac{R^2}{4}}}=\frac{2}{\sqrt{5}}$
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con lăc đơn !
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Bai nay co lien quan den lop 11 ve luc LorenxoDau tien ta tinh van toc cuc dai trong qua trinh dao dong cua vat $v_{max}=\sqrt{2gl(1-cos\alpha _{o})}=\sqrt{0,2} m/s$Neu khong dat trong tu truong thi luc cang day cuc dai la $T_{1}=mg(3-2cos\alpha _{o})=1.02N$Khi dat trong tu truong ta co $Tmax=T_{1}+F_{Lorenxo}=T_{1}+B.v_{max}.q=$
Bai nay co lien quan den lop 11 ve luc LorenxoDau tien ta tinh van toc cuc dai trong qua trinh dao dong cua vat $v_{max}=\sqrt{2gl(1-cos\alpha _{o})}=\sqrt{0,2} m/s$Neu khong dat trong tu truong thi luc cang day cuc dai la $T_{1}=mg(3-2cos\alpha _{o})=1.02N$Khi dat trong tu truong ta co $Tmax=T_{1}+F_{Lorenxo}=T_{1}+B.v_{max}.q=1,04 (N)$ Den day chon dk dap an B roi do. Tinh them chu ki de ro.....................
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moi nguoi oi giai giup minh nhe
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Ta tinh dk $AC=6\sqrt{2}=CB va OB=6$Goi khoang cach tu M den A va B la $d_{1}$ va khoang cach tu C den M la $d_{2}$Pt do 2 song tu A va B gui toi M la $u_{AM}=u_{BM}=2a.cos(wt-\frac{2\pi d_{1}}{\lambda })$Pt do song tu C gui toi M la $u_{CM}=a.cos(wt-\frac{2\pi d_{2}}{\lambda })$De M dao dong vs bien do la $5a=2a+2a+a$ thi cac song tu nguon truyen toi M cung phaKhi do $\frac{2\pi (d_{1}-d_{2})}{\lambda }=k2\pi $De OM min thi $d_{1}-d_{2}=\lambda =1,2$Khi do $\sqrt{x^{2}+OB^{2}}-(CO-x)=1,2$ vs $OM=x$ $\sqrt{x^{2}+36}-(6-x)=1,2$ De dang tinh dk $x=1,1cm$Dap an $C$
Ta tinh dk $AC=6\sqrt{2}=CB va OB=6$Goi khoang cach tu M den A va B la $d_{1}$ va khoang cach tu C den M la $d_{2}$Pt do 2 song tu A va B gui toi M la $u_{AM}=u_{BM}=2a.cos(wt-\frac{2\pi d_{1}}{\lambda })$Pt do song tu C gui toi M la $u_{CM}=a.cos(wt-\frac{2\pi d_{2}}{\lambda })$De M dao dong vs bien do la $5a=2a+2a+a$ thi cac song tu nguon truyen toi M cung phaKhi do $\frac{2\pi (d_{1}-d_{2})}{\lambda }=k2\pi $De OM min thi $d_{1}-d_{2}=\lambda =1,2$Khi do $\sqrt{x^{2}+OB^{2}}-(CO-x)=1,2$ vs $OM=x$ $\sqrt{x^{2}+36}-(6-x)=1,2$ De dang tinh dk $x=1,1cm$Dap an $A$
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sửa đổi
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phản ứng hạt nhân
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Goi goc can tim la $\alpha$ thiTheo dinh ly ham sin co $\frac{m_{p}.v_{p}}{sin(180-2\alpha )}=\frac{m_{He}.v_{He}}{sin\alpha }$ $<=>\frac{sin^{2}\alpha }{sin^{2}2\alpha }=\frac{m_{He}.K_{He}}{m_{p}.K_{p}}$Lai theo bao toan nang luong co $K_{p}=2K_{He}$Theo do $ \frac{sin^{2}\alpha }{sin^{2}2\alpha }=\frac{1}{2}.4=2$Tu do tinh dk $\alpha =45^{o}$
Goi goc giua hat He va proton la $\alpha$ thiTheo dinh ly ham sin co $\frac{m_{p}.v_{p}}{sin(180-2\alpha )}=\frac{m_{He}.v_{He}}{sin\alpha }$ $<=>\frac{sin^{2}\alpha }{sin^{2}2\alpha }=\frac{m_{He}.K_{He}}{m_{p}.K_{p}}$Lai theo bao toan nang luong co $K_{p}=2K_{He}$Theo do $ \frac{sin^{2}\alpha }{sin^{2}2\alpha }=\frac{1}{2}.4=2$Tu do tinh dk $\alpha =69,29^{o}$Vay goc can tim la $2\alpha =138,59^{o}$
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1
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Xem chi tiet tai Ly/Hoctainha.vn/Hoi-Dap/Cau-Hoi/5718/khovay/5699#5699Cau nay minh giai cho Pooh oy.
Xem chi tiet tai Ly.Hoctainha.vn/Hoi-Dap/Cau-Hoi/5718/khovay/5699#5699Cau nay minh giai oy
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sửa đổi
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giup nhe
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Ta gia su vat 1 dao dong vs $x_{1}=4cos(wt)$Khi do vat 2 dao dong vs pt $x_{2}=2cos(wt+\frac{\pi }{3})$Khoang cach giua 2 vat la $x=x_{1}+x_{2}=\sqrt{28} cos(wt+0.106\pi )$Khoang cach cuc dai giua 2 vat chinh la bien do cua giao dong tong hop $x$ nhu trenVay khoang cach Max la $\sqrt{28} cm$
Ta gia su vat 1 dao dong vs $x_{1}=4cos(wt)$Khi do vat 2 dao dong vs pt $x_{2}=2cos(wt+\frac{\pi }{3})$Khoang cach giua 2 vat la $x=x_{1}-x_{2}=2\sqrt{3} cos(wt-\frac{\pi }{6} )$Khoang cach cuc dai giua 2 vat chinh la bien do cua giao dong tong hop $x$ nhu trenVay khoang cach Max la $2\sqrt{3} cm$
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sửa đổi
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Điện xoay chiều
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cai nay cung hay dayDo $u_{AN} $ vuong pha $u_{MB} va u_{AB}$ lech pha $\frac{\pi }{3}$ vs $u_{AN}$ nen $u_{AB}$ lech $\frac{\pi }{6}$ vs $u_{MB}$Sau do dung cong thuc tong hop vec to thi $ \overrightarrow{u_{AB}}-\overrightarrow{u_{MB}}=\overrightarrow{u_{AM}}$tu do suy ra $u_{AB}$ lech pha $\frac{\pi }{6}$ so vs $u_{AM}$ hay $u_{R}$ hay dong dien trong mach va cung suy ra dk $U_{AM}=120V$Do $P=UIcos \Phi=>I=\frac{P}{Ucos\Phi }=2A $tinh ngay dk $R=\frac{U_{AM}}{I}=60\Omega $ Tu gian do thi $u_{AN} $ lech pha $\frac{\pi }{6}$ so vs $u_{R}$ suy ra $Z_{C}=\frac{R}{\sqrt{3} }=\frac{60}{\sqrt{3} }=20\sqrt{3}\Omega $Khi noi tat cuon day thi $P=\frac{U^{2}R}{R^{2}+Z^{2}_{C}}=180W$
cai nay cung hay dayDo $u_{AN} $ vuong pha $u_{MB} va u_{AB}$ lech pha $\frac{\pi }{3}$ vs $u_{AN}$ nen $u_{AB}$ lech $\frac{\pi }{6}$ vs $u_{MB}$Sau do dung cong thuc tong hop vec to thi $ \overrightarrow{u_{AB}}-\overrightarrow{u_{MB}}=\overrightarrow{u_{AM}}$tu do suy ra $u_{AB}$ lech pha $\frac{\pi }{6}$ so vs $u_{AM}$ hay $u_{R}$ hay dong dien trong mach va cung suy ra dk $U_{AM}=120V$Do $P=UIcos \Phi=>I=\frac{P}{Ucos\Phi }=2A $tinh ngay dk $R=\frac{U_{AM}}{I}=60\Omega $ Tu gian do thi $u_{AN} $ lech pha $\frac{\pi }{6}$ so vs $u_{R}$ suy ra $Z_{C}=\frac{R}{\sqrt{3} }=\frac{60}{\sqrt{3} }=20\sqrt{3}\Omega $Khi noi tat cuon day thi $P=\frac{U^{2}R}{R^{2}+Z^{2}_{C}}=540W$
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