Thả một hòn đá rơi từ miệng một cái hang sâu xuống đến đáy. Sau 5 s kể từ lúc bắt đầu thả thì nghe tiếng hòn đá chạm vào đáy. Biết vận tốc truyền âm trong không khí là 330 m/s. Lấy g = 9,8 m/s2. Chiều sâu của hang là
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Ta có: $t_1 + t_2 = 5$ (1)
Quãng đường hòn đá rơi xuống đáy hang là: $h = \frac{1}{2}gt_1^2 = \frac{1}{2} * 9.8 * t_1^2 = 4.9t_1^2$ (2)
Quãng đường âm thanh truyền từ đáy hang lên miệng hang là: $h = v_{sound} * t_2 = 330t_2$ (3)
Từ (2) và (3) suy ra: $4.9t_1^2 = 330t_2$ (4)
Từ (1) suy ra: $t_2 = 5 - t_1$ (5)
Thay (5) vào (4) ta được: $4.9t_1^2 = 330(5 - t_1) \Leftrightarrow 4.9t_1^2 + 330t_1 - 1650 = 0$
Giải phương trình bậc hai trên, ta được nghiệm dương: $t_1 \approx 4.701 s$
Thay $t_1$ vào (2) ta được: $h = 4.9 * (4.701)^2 \approx 108.24 m$
Câu hỏi liên quan
Mark the letter A, B, C, or D on your answer sheet to indicate the best arrangement of utterances or sentences to make a meaningful exchange or text in each of the following questions from 13 to 17
a. Mr Willis: It was announced on TV that a new wildlife park will open to the public next week. Would you like to visit it?
b. Mr Willis: Simon, I've just heard some good news.
c. Simon: What's it about, Dad?
Trong Access, muốn tạo liên kết giữa hai bảng thì hai bảng đó phải có hai trường thỏa mãn điều kiện gì?
Phần lãnh thổ trung tâm Bắc Mỹ địa hình phân hoá đa dạng được phân ra thành khu vực nào dưới đây?
Read the following passage about reading skill and mark the letter A, B, C or D on your answer sheet to indicate the option that best fits each of the numbered blanks from 18 to 22
Reading is an essential skill that enhances our cognitive abilities in many ways. Firstly, it improves our language skills. When we read, we learn new words and understand how they are used in context, ___(18)___. This helps in expanding our vocabulary and improving our communication skills. Secondly, reading boosts our imagination and creativity. ___(19)___, it takes us to different worlds and situations we might not experience in real life. This stimulates our creativity and helps us think outside the box. Thirdly, regular reading enhances our concentration and focus. It requires us to pay attention to details and follow complex narratives, ___(20)___. Additionally, reading provides us with knowledge about various subjects and cultures. It allows us to gain insights into ___(21)___. This broadens our perspective and helps us become more empathetic and understanding. Finally, reading is a great way to relax and de-stress. It can be a form of escapism, where we can lose ourselves in a story and forget about our daily worries, which provides a much-needed break for us. In conclusion, reading is not just a leisure activity. It plays a significant role in our cognitive development, helping us to ___(22)___. Therefore, it's important to cultivate a habit of reading from a young age.
Cho tập hợp M = {x ∈ ℝ | x là ước chung của 12 và 20}. Tổng S các phần tử của tập hợp M là:
Read the following leaflet and mark the letter A, B, C or D on your answer sheet to indicate the option that best fits each of the numbered blanks from 7 to 12.
Grand Opening of TIEU MINH Supermarket!
Welcome to the brand-new TIEU MINH Supermarket, where unbeatable offers await you! Join us as we celebrate our grand opening with special deals and discounts on a wide (7)_______of essentials, from groceries to household appliances and more!
Here’s what you can look forward to:
• Amazing discounts on a vast amount of products, including fresh foods, kitchenware, storage solutions, and (8)______ items.
• Exclusive “Buy One, Get the Other at 20% Off” deals on select items.
• A lucky draw with the chance to win (9)______for your home, perfect for upgrading your storage and kitchen spaces!
(10)______high prices, the items will be offered at a 30-50% discount without compromising quality. (11)______at our grand opening event to enjoy free samples, interactive games, and live demos from top brands. Our rewards program also lets you earn points and receive exclusive member(12)_______.
Nguyên nhân chủ yếu nào làm cho khu vực Mỹ Latinh có tỉ lệ dân cư đô thị cao?
Choose a suitable word or phrase (marked A, B, C, or D) to fill in each blank.
The firm spent thousands dollars wining and dining ____________ clients.
Cho ba mệnh đề như sau:
A: “ABCD là hình chữ nhật”.
B: “AB = CD”.
C: “ABCD là hình bình hành”.
Mệnh đề nào sau đây sai?
Trong các thí nghiệm sau thí nghiệm nào không phải là phép thử ngẫu nhiên:
Có mấy phương pháp ủ phân?
Cho biết thông tin là gì?
Cho ba nguyên tử có kí hiệu là \({}_{12}^{24}Mg,{}_{12}^{25}Mg,{}_{12}^{26}Mg\). Phát biểu nào sau đây là sai?
Toán học có vai trò như thế nào đối với việc nghiên cứu Vật lí.
Mark the letter A, B, C or D on your answer sheet to indicate the best arrangement of utterances or sentences to make a meaningful exchange or text in each of the following questions.
a. Sally: Watch out, Janna! That floor looks really slippery.
b. Janna: Oh, thanks for warning me, Sally. I’ll be extra careful.
c. Sally: Good idea. Better safe than sorry!
Đăng tải thông tin cá nhân trên mạng gây ra hậu quả nào sau đây?
Read the passage carefully. Choose an option (A, B, C or D) that best answers each question from 16 to 22.
1. Like many emergency responders, Nicholas Groom is used to stress at work. On the one hand, the stress can be helpful. “I find that when attending a serious incident, it helps me to maintain focus on the situation,” Nicholas Groom said. On the other hand, the work can be highly pressurized. “Too much stress can impair your ability to make decisions,” he adds. And Groom is not alone in his complicated relationship with stress.
2. Many people believe that there should be a balanced amount of stress. In other words, not too much stress so you’re not overwhelmed but not too little stress so you don’t feel unmotivated. After all, some anxiety is motivating; think of the adrenaline before a deadline or the excitement before a competition. Sports fans sometimes even talk about a “gene” in some athletes who seem to play best in the decisive final moments of a match. Furthermore, many psychologists claim that performance in many situations increases with stress up to a point. Of course, any stress can cause harm when it’s prolonged. To take just one example, a long-term high heart rate is linked to cardiovascular diseases. And additional stressors, such as financial pressures or psychiatric issues, clearly affect how beneficially someone can respond to stress.
3. So is there a way to harness stress to your advantage while being mindful of its detrimental long-term effects? One key factor is to avoid, whenever possible, the point when stress leads to mental and physical collapse. Crystal Wernicke, 30, has always used stress as a motivator. But juggling between parenting, a full-time job, a voluntary role and financial troubles at the same time became too much and eventually led to a two-month period of illness. Another factor is the presence of control. For those who feel powerless over their situation, stress is unlikely to be beneficial. But with some autonomy over stressful tasks, we are better able to convert that pressure into higher performance.
4. When it comes to stress and how it affects your performance, it’s helpful to recognize the variations in personality, type of stress and task that affect the level of pressure you are under, as well as understanding tools you can use to control and harness that stress. Ultimately, it’s not helpful to take a one-sided view, either demonizing or glorifying stress. As James C Quick, a management professor at the University of Texas, sums up: “Stress can be the kiss of death as well as the spice of life.”
Why was Crystal Vernicke sick for two months?
Hiện nay, dân số Hoa Kì đứng thứ mấy trên thế giới?
Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word in the following question.
The teacher is considering whether to choose Nike or Jackie as class president.
Parabol \((P):y = {x^2} - 3x + 5\) có tổng số điểm chung với 2 trục là?