\(x=3sin\omega t=3Acos\left(\omega t-\dfrac{\pi}{2}\right)+4Acos\omega t\) => Hai dao động vuông pha.

Biên độ dao động của vật là \(A'=\sqrt{\left(3A\right)^2+\left(4A\right)^2}=5A\)

Chúc các bạn tham gia thi đạt kết quả cao, cuộc thi diễn ra thành công tốt đẹp nhé ^^

Okeeee e ui, a sẽ cố gắng hết sức, có gì gửi bản kế hoạch qua H24 cho a hoặc kb face với a nha. 

fb.com/its.justoreo10

Giá như được góp mặt làm BGK :( 

Try something new :D

Fill in suitable words.

1. I don't like to read _a_ _ _ _ _ newspapers because they're full of lies, scandal and gossip.

2. Nguoi Phan Xu is a film making a _a_ _ _ _ _ impression on its audiences all over Vietnam.

3. Don't keep me in dark, tell me now! I can't bear the _u_ _ _ _ _ _.

4. 'Chung Ta Cua Hien Tai' was _ _m_ _ _ _ _d for 'Best MV Making' reward in WECHOICE this year.

5. 'We of the present, spent our youth together without thinking. To be s_ _ _ _f_ _ _ _ _ other or not in the future, don't forget that we spent all the best things together. Love you'.

6. A serious conflict made it possible for him to heal the _r_ _ _h.

7. Haiyan Typhoon, which occured in Phillipines 8 years ago, is considered one of the most powerful tropical cyclones ever _ _c_ _ _ _ _.

8. We must see which way the wind blows before _ _ _ _ _ _ _ _ _ _g somebody. The truth may not what we see.

9. My favourite drink at the bar was Blue Tequila, but now I _ _ _ _ _ _ to drink Matcha Green Cocktail because its taste is much more better.

10. We should believe in him, he comes highly recommended not because of eventuality. He will face the _ _ _ _ _ and get over from all.

Câu này lạ nhỉ, thử ADCT E=U/d = 110/(8,8x10^-4) = 125000(V/m).

Vậy Emax = 125000V/m.

Cảm kháng \(Z_L=Lw=\dfrac{1}{\pi}\cdot100\pi=100\left(\Omega\right)\)

Dung kháng \(Z_C=\dfrac{1}{Cw}=\dfrac{1}{\dfrac{10^{-4}}{2\pi}\cdot100\pi}=200\Omega\)

\(\varphi=\varphi_u-\varphi_i=0-\dfrac{\pi}{4}=-\dfrac{\pi}{4}\)

\(tan\varphi=\dfrac{Z_L-Z_C}{R}\Leftrightarrow tan\dfrac{-\pi}{4}=\dfrac{100-200}{R}\Rightarrow R=100\left(\Omega\right)\)

a) Ta thấy N1 > N2  => đây là máy hạ áp.

b) \(\dfrac{N_2}{N_1}=\dfrac{U_2}{U_1}\Leftrightarrow\dfrac{250}{1000}=\dfrac{U_2}{500}\Rightarrow U_2=125\left(V\right)\)

Dung kháng \(Z_C=\dfrac{1}{Cw}=\dfrac{1}{\dfrac{10^{-4}}{\pi}\cdot100\pi}=100\left(\Omega\right)\)

Tổng trở \(Z=\sqrt{R^2+Z_C^2}=\sqrt{100^2+100^2}=100\sqrt{2}\left(\Omega\right)\)

Hệ số công suất \(cos\varphi=\dfrac{R}{Z}=\dfrac{100}{100\sqrt{2}}=\dfrac{\sqrt{2}}{2}\)