Dùng một dao vòng có thể tích 50cm3 để lấy mẫu đất nguyên dạng, khối lượng đất ẩm là 95g, khối lượng sau khi sấy khô là 75g, tỷ trọng hạt đất 2,68. Trọng lượng riêng của
nước 9,8kN/m3

. Hãy xác định:
- Trọng lượng thể tích tự nhiên
- Độ ẩm
- Hệ số rỗng
- Độ bảo hòa

Rosa records the distance that a toy car rolls and the time it takes to cover the distance. what scientific practice is this? collecting data asking a question providing explanations communicating results

Which of the following explains why it took so long for the public to accept the negative health effects of smoking? a)people were waiting for counter reasons, and those were presented.b)scientists had not completely finalized their results, which took 30 years.c)cigarettes were cheaply available and media channels were very inefficient.d)cigarette manufacturers were trying hard to bring an alternative into the market

Consider the particle-in-a-box problem in 1d. a particle with mass m is confined to move freely between two hard walls situated at x = 0 and x = l. the potential energy function is given as (a) describe the boundary conditions that must be satisfied by the wavefunctions ψ(x) (such as energy eigenfunctions). (b) solve the schr¨odinger’s equation and by using the boundary conditions of part (a) find all energy eigenfunctions, ψn(x), and the corresponding energies, en. (c) what are the allowed values of the quantum number n above? how did you decide on that? (d) what is the de broglie wavelength for the ground state? (e) sketch a plot of the lowest 3 levels’ wavefunctions (ψn(x) vs x). don’t forget to mark the positions of the walls on the graphs. (f) in a transition between the energy levels above, which transition produces the longest wavelength λ for the emitted photon? what is the corresponding wavele