Hai vật được thả rơi tự do đồng thời từ hai độ cao khác nhau h1 và h2. Khoảng thời gian rơi của vật thứ nhất bằng một nửa khoảng thời gian rơi của vật thứ hai. Bỏ qua lực cản của không khí. Tỉ số các độ cao h2h1 bằng
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Công thức tính độ cao khi rơi tự do là $h = \dfrac{1}{2}gt^2$.
Ta có: $h_1 = \dfrac{1}{2}gt_1^2$ và $h_2 = \dfrac{1}{2}gt_2^2$.
Suy ra: $\dfrac{h_1}{h_2} = \dfrac{\dfrac{1}{2}gt_1^2}{\dfrac{1}{2}gt_2^2} = \dfrac{t_1^2}{t_2^2} = \left(\dfrac{t_1}{t_2}\right)^2 = \left(\dfrac{1}{2}\right)^2 = \dfrac{1}{4} = 0,25$.
Vậy tỉ số $\dfrac{h_1}{h_2} = 0,25$
Câu hỏi liên quan
Một bộ acquy có thể cung cấp dòng điện 4A liên tục trong 2 giờ thì phải nạp lại. Tính cường độ dòng điện mà acquy này có thể cung cấp liên tục trong 40 giờ thì phải nạp lại.
Read the following passage about food addiction and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.
Few people would disagree that one of the world's most popular dishes is pizza. Twenty-two-year-old Zack certainly wouldn't. He would eat a variety of pizza-based items, including homemade pizza, precooked microwave pizza, and even pizza leftovers from the night before. He was consuming 800kg of pizza a year. As a child, Zack had eaten a wide variety of food. But he became addicted to pizza when he started secondary school. American school meals have often been criticised for the large amount of fast food present on the menu, and pizza is the star dish. Zack even spent all his pocket money on slices of pizza.
Naturally, Zack's family worried about his high-calorie, low-vitamin diet. So did Zack. In an attempt to break his addiction, Zack agreed to appear on a TV programme called Freaky Eaters. Its aim was to encourage food addicts to beat their addictions with the help of a psychologist and nutritionist. It wasn't easy. He had to eat a fish dish, while his brother sat in front of him enjoying... a pizza! However, Zack met the challenge and has never eaten pizza again.
Seventeen-year-old Stacy Irvine's friends visit her and discover that she has been rewarded thousands of free toys from fast food restaurants as a regular customer. Stacy's mother often gave her two-year-old girl a portion of fried chicken in a McDonald's restaurant. [I] Since then, Stacy has refused to eat anything else except for pieces of fried chicken, and as a result, her diet has created serious health. She has been warned that if she doesn't change her diet, she will die. [II] Stacy once collapsed due to lack of vitamins and nutrients and needed to be hospitalised. [III] She insisted that Stacy adopt a healthier lifestyle. However, worryingly, Stacy's mother said that while Stacy was beginning to understand the seriousness of her situation, she couldn't eat anything else but chicken nuggets. [IV]
Twenty-year-old Hanna Little was keen on chips. The only thing that Hanna consumed for fifteen years was one plate of chips after another. Not surprisingly, a diet that contained few nutrients and an excess of fat and carbohydrates could only have negative consequences. And it did because not only did Hanna develop health problems, but she also had to leave her job after collapsing at work. At five, Hanna became addicted to chips and refused to eat fruits and vegetables despite her mother's efforts. Hanna says that she was terrified of tasting the flavour of different types of food and she would feel anxious just at the idea of doing it. Parties, picnics and barbecues with friends and family used to be a nightmare. Furthermore, Hanna was soon seen as 'odd' by her friends' parents.
It wasn't until the age of sixteen that Hanna realised she had Selective Eating Disorder (SED). Despite this new knowledge, no solution was found. It wasn't until she lost her job before she started eating normally. Hanna sought therapy from psychologist Felix Economakis, who used hypnosis, a treatment that none of the doctors that she had seen before had mentioned, to get her to eat fruit after one one-hour session, and since then she has been willing to eat anything.... including chips!
(Adapted from Friends Global)
Which of the following is TRUE according to the passage?
Quá trình toàn cầu hóa mang lại cơ hội nào dưới đây đối với các nước đang phát triển?
Muối dưa có bản chất là quá trình nào sau đây xảy ra?
Read the following advertisement 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 1 to 6:
JOIN THE FITNESS REVOLUTION
Are you looking to get ___(1)___ shape but don’t know where to start? Our online fitness platform gives you access to the best workouts to fit your schedule. Whether you prefer yoga, cardio, or strength training, we’ve got something for everyone. You can ___(2)___ our workouts anytime, anywhere, without needing any special equipment. Plus, our expert trainers are always available to help ___(3)___ your form and provide tips for improvement. Don't wait to ___(4)___ your fitness goals – sign up today and enjoy a free month of workouts! No matter your fitness level, you'll ___(5)___ results and feel better than ever. Remember, your journey ___(6)___ with the first step.
Ngành nghề nào dưới đây không thuộc nhóm ngành sinh học cơ bản?
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.
Albert Einstein: A Genius Who Shaped Science
Albert Einstein has always been renowned for (7)______ of groundbreaking theories. His discoveries not only gained recognition worldwide but also made headlines in the scientific community, strengthening his status as one of the most respected (8) ______ in the history of physics.
His ability to think outside the box led to theories that challenged conventional understanding and reshaped the field. Einstein is often associated with the theory of relativity, a revolutionary concept that transformed our understanding of space, time, and gravity.
(9)______ facing initial skepticism, Einstein's theories eventually gained widespread acceptance and earned him the admiration of many scientists. Today, countless researchers (10)_______ to him as an inspiration.
His unparalleled (11)______ into science continue to make a huge contribution to scientific progress. (12)______significant impact of his work is its influence on modern technology, from GPS systems to nuclear energy. Einstein’s legacy is admired by generations, proving the power of curiosity and determination.
Chính phủ hoạt động theo mấy hình thức chủ yếu?
Xác định: Biểu đồ theo nhận định thích hợp nhất thể hiện giá trị xuất khẩu của các quốc gia là?
Số đường thẳng đi qua điểm và tiếp xúc với đồ thị hàm số là?
Nội dung nào sau đây là một trong những tiêu chuẩn cơ bản để nhận diện văn minh?
Đôn Ki-hô-tê là tác phẩm văn học nổi tiếng của tác giả nào?
Trong các thí nghiệm sau:
Thí nghiệm 1: Cho barium vào dung dịch zinc chloride \(\left( \text{ZnC}{{\text{l}}_{2}} \right)\) dư.
Thí nghiệm 2: Cho iron (II) chloride tác dụng với dung dịch silver nitrate dư.
Thí nghiệm 3: Điện phân dung dịch copper (II) sulfate.
Thí nghiệm 4: Dẫn khí hydrogen qua aluminium oxide nung nóng.
Các thí nghiệm thu được kim loại sau khi phản ứng kết thúc là:
Nhà nước Trung Hoa thời kì cổ - trung đại được tổ chức theo mô hình nào?
GPS và bản đồ số dùng không có chức năng nào sau đây?
Phát biểu nào sau đây không đúng khi nói về vai trò của hóa học trong đời sống?
Hợp chất MX2 có tổng số hạt mang điện là 44. Trong hợp chất, số hạt proton của nguyên tử X nhiều hơn số hạt proton của nguyên tử M là 10 hạt. Cấu hình electron thu gọn của X là
- Cho A = {1; 2; 3}. Trong các khẳng định sau, khẳng định nào sai?
Em hãy cho biết thiết kế mạch điện tử được tiến hành theo mấy bước:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.
Biting into a ripe, juicy fruit brings a smile to many people’s faces. But eating that same fruit a week before it is ripe probably wouldn’t be as enjoyable! Unripe fruits are often hard and bitter, but that serves a purpose. The hard exterior of an unripe fruit protects the developing seed inside. After a seed fully develops inside the fruit, the fruit changes color, softens, and gets sweeter to become more attractive to animals and humans. These organisms eat the fruit and spread its seeds, ensuring the plant’s survival and regrowth.
But how does a fruit ripen? The ripening process involves many complex chemical reactions. When a fruit ripens, it goes through a chemical change. A chemical change happens when bonds within molecules break, and the atoms that once formed them regroup into new molecules. Chemical changes are irreversible. Once a fruit ripens, it cannot become unripe again.
One molecule responsible for this chemical change is ethylene. Ethylene (C2H4) is a colorless gas made up of carbon and hydrogen atoms. (I). It is a naturally occurring molecule in the atmosphere. (II). It is also an important plant hormone. (III). Plants release ethylene through the growing tips of roots, flowers, and ripening fruit. (IV). Although ethylene serves other purposes in plants, one of its main purposes is to trigger the chemical reactions that cause fruits to ripen. As the fruit matures, oxygen in the air helps stimulate the production of ethylene. This ethylene production is a signal that begins fruit ripening. For that reason, unripe fruits have low levels of ethylene, while ripe fruits have higher levels of ethylene. Most fruits produce ethylene and respond to ethylene in the atmosphere.
Although fruits require ethylene to ripen, different types of fruits respond to this molecule in two distinct ways: non-climacteric fruits and climacteric fruits. Non-climacteric fruits do not ripen after harvesting. They produce very little ethylene of their own. Climacteric fruits, on the other hand, continue to ripen after they are picked. These fruits produce a large amount of ethylene. Climacteric fruits can also speed up the ripening process of other fruits nearby since they release high levels of ethylene into the air.
Which of the following best summarizes the main point of the passage?
