Đổi: \(50cm^2=0,0005m^2\)

Trọng lượng: \(P=F=10m=10.50=500\left(N\right)\)

Áp suất của bao gạo lên mặt sàn là:

\(p=\dfrac{f}{S}=\dfrac{500}{0,0005}=1000000\left(Pa\right)\)

\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}\Rightarrow\dfrac{x^2}{4}=\dfrac{y^2}{9}=\dfrac{z^2}{16}\)

Áp dụng t/c dtsbn:

\(\dfrac{x^2}{4}=\dfrac{y^2}{9}=\dfrac{z^2}{16}=\dfrac{x^2+y^2+z^2}{4+9+16}=\dfrac{116}{29}=4\)

\(\Rightarrow\left\{{}\begin{matrix}x^2=4.4=16\\y^2=4.9=36\\z^2=16.16=16^2\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=4\\y=6\\z=16\end{matrix}\right.\\\left\{{}\begin{matrix}x=-4\\y=-6\\z=-16\end{matrix}\right.\end{matrix}\right.\)

1D  2C

Tần số: \(f=\dfrac{20}{2}=10\left(Hz\right)\)

Tốc độ góc là: \(\omega=2\pi f=20\pi\left(rad/s\right)\)

Tốc độ dài của chất điểm: \(v=\omega R=20\pi.1=20\pi\left(m/s\right)\)

Chọn C do \(x^2\ge0>-16\forall x\)

1 There isn't an Indian restaurant here

Is there an Indian restaurant here?

2 There aren't five cars in the park

Are there five cars in the park?

3 There isn't a sandwich bar on the table

Is there a sandwich bar on the table?

11. Drinking this water is not safe. 
 It’s not ____safe to drink this water__________________________ .
12. Swimming across this river is dangerous. 
 It is____dangerous to swim across this river______________ .
13. To do this exercise is not easy. 
 It’s ___difficult to do this exercise______

Câu 4 là isn't nha

1 There is

2 There is

3 There is

4 There arent't

5 There are/ there are

6 Are there