K
Khách

Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.

HỎI TIẾN

2 tháng 3

jycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszgeajycjtiuyodfgfdxuhfxthtgjhgfhgfchgfhfjycrszg...

19 tháng 10 2016

 Bn ơi viết sai rồi,19/10 nhé

19 tháng 10 2016

mai mới 20/10

 

29 tháng 10 2025

Câu 1: Khi xe ô tô chạy đều trên đường nằm ngang, vận tốc không thay đổi nên gia tốc bằng 0. Lực kéo của động cơ cân bằng các lực cản lăn và cản không khí. Câu 2: Trong chuyển động thẳng biến đổi đều, gia tốc a được tính bằng tỷ số độ thay đổi vận tốc chia cho thời gian, a = (delta v)/(delta t). Do đó tỷ số (delta t)/(delta v) chỉ là nghịch đảo của gia tốc, cho biết thời gian cần để thay đổi mỗi đơn vị vận tốc.

25 tháng 4 2016

Lực ma sát

Lực ma sát

hoặc      image413

Gốc toạ độ tại vị trí xe có v= 100km/h \(\approx\) 27,8m/s.

Mốc thời gian tại  lúc bắt đầu hãm xe.

Theo định luật II Niu-tơn và công thức tính Fms , ta được:

    image012.gif

a) Khi đường khô \(\mu\) = 0,7 \(\Rightarrow\) a = - 0,7.10 = - 7(m/s2)

Quãng đường xe đi được là: v2 – v02 = 2as \(\Rightarrow\)  s = image014.gif

b)  Khi đường ướt \(\mu\) = 0,5 \(\Rightarrow\) a = -0,5.10 = - 5(m/s2).

Quãng đường xe đi được là: s =image016.gif»77,3(m).

10 tháng 10 2019

2) ta có : \(\left\{{}\begin{matrix}v_0+a\left(3-\frac{1}{2}\right)=8\\v_0+a\left(6-\frac{1}{2}\right)=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}v_0+\frac{5}{2}a=8\\v_0+\frac{11}{2}a=2\end{matrix}\right.\)

<=> \(\left\{{}\begin{matrix}-3a=6\\v_0+\frac{5}{2}a=8\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}a=-2\left(m/s^2\right)\\v_0=13m/s\end{matrix}\right.\)

=> Chọn D.

10 tháng 10 2019

Bài1:

\(S_1=v_0.2-\frac{1}{2}.a2^2=20\)

=> \(2v_0-2a=60\)(1)

\(v^2-v_0^2=2as\Rightarrow0^2-v_0^2=2a.20\Rightarrow v_0=\sqrt{40a}\)(2)

Từ (1) và (2) => \(2.\sqrt{40a}-2a=60\)

=> \(2\left(\sqrt{40a}-a\right)=60\)

<=> \(\sqrt{40a}-a=30\)

<=> \(\sqrt{40a}=30+a\Leftrightarrow40a=a^2+60a+900\)

=> \(a^2+20a+900=0\) (pt vô nghiệm)

Đổi khối lượng: $m = 3000\text{ g} = 3\text{ kg}$. Chọn gốc thế năng tại mặt đất.

a) Cơ năng ban đầu của vật

Tại độ cao cực đại $z_0 = 30\text{ m}$, vật có vận tốc $v_0 = 0$:

$$W = W_t + W_đ = mgz_0 + 0 = 3 \cdot 10 \cdot 30 = 900 \text{ (J)}$$

b) Vận tốc cực đại của vật

Vận tốc cực đại khi vật chạm đất (thế năng bằng 0, cơ năng bảo toàn):

$$W = \frac{1}{2}mv_{max}^2 \Rightarrow 900 = \frac{1}{2} \cdot 3 \cdot v_{max}^2 \Rightarrow v_{max} = \sqrt{600} \approx 24,49 \text{ (m/s)}$$

c) Vị trí của vật khi có vận tốc 18 km/h

Đổi vận tốc: $v = 18\text{ km/h} = 5\text{ m/s}$.

Bảo toàn cơ năng:

$$W = mgz + \frac{1}{2}mv^2 \Rightarrow 900 = 3 \cdot 10 \cdot z + \frac{1}{2} \cdot 3 \cdot 5^2$$$$\Rightarrow 900 = 30z + 37,5 \Rightarrow 30z = 862,5 \Rightarrow z = 28,75 \text{ (m)}$$

d) Vị trí vật có động năng bằng 1/3 lần thế năng

Theo đề bài: $W_đ = \frac{1}{3}W_t$.

Bảo toàn cơ năng:

$$W = W_t + W_đ = W_t + \frac{1}{3}W_t = \frac{4}{3}W_t$$$$\Rightarrow 900 = \frac{4}{3} \cdot (mgz) \Rightarrow 900 = \frac{4}{3} \cdot (3 \cdot 10 \cdot z) \Rightarrow 900 = 40z \Rightarrow z = 22,5 \text{ (m)}$$