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相关概念视频

Constant Volume Calorimetry02:41

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant (atmospheric) pressure and are convenient to measure heat flow (or enthalpy change) accompanying processes that occur in solution at constant pressure. A different type of calorimeter that operates at constant volume, colloquially known as a bomb calorimeter, is used to measure the energy produced by reactions that yield large amounts of heat and...
Radioactive Decay and Radiometric Dating02:48

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
Nuclear Transmutation03:20

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed protons being...
Impulse01:13

Impulse

According to Newton’s second law of motion, the rate of change of the momentum of an object is the net external force acting on it. The total change in momentum between two timepoints thus depends on both the external force acting on it and the time over which it acts. Describing this mathematically, the total change of an object’s motion is proportional to the force vector and the time over which it is applied. This product is called impulse.
Additionally, it can be shown that the total...
Types of Collisions - II01:19

Types of Collisions - II

When two or more objects collide with each other, they can stick together to form one single composite object (after collision). The total mass of the object after the collision is the sum of the masses of the original objects, and it moves with a velocity dictated by the conservation of momentum. Although the system's total momentum remains constant, the kinetic energy decreases, and thus such a collision is an inelastic collision. Most of the collisions between objects in daily life are...
Impact: Problem Solving01:26

Impact: Problem Solving

In an experiment conducted during a Mars mission, a rover propels a projectile with an initial velocity, and the projectile rebounds after colliding with the Martian surface. To ascertain the maximum height attained by the projectile after this collision, the known restitution coefficient and acceleration due to gravity are employed.
By designating the launch point as the origin and utilizing kinematic equations, the vertical component of the projectile's velocity at the point of impact is...

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相关实验视频

Updated: Jul 8, 2026

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System
09:44

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

Published on: June 5, 2014

月球撞击历史从 (40) Ar/(39) Ar 玻璃球体的约会.

Culler1, Becker, Muller

  • 1Department of Geology and Geophysics, Department of Physics, University of California, Berkeley, CA 94720, USA. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, U.

Science (New York, N.Y.)
|March 10, 2000
PubMed
概括
此摘要是机器生成的。

月球球体分析显示,撞击坑形成速度在35亿年内波动. 最近月球撞击的增加与地球相关.

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Production of Synthetic Nuclear Melt Glass
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Fluid-cell Raman Spectroscopy for operando Studies of Reaction and Transport Phenomena during Silicate Glass Corrosion

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Last Updated: Jul 8, 2026

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System
09:44

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

Published on: June 5, 2014

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Fluid-cell Raman Spectroscopy for operando Studies of Reaction and Transport Phenomena during Silicate Glass Corrosion
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科学领域:

  • 月球地质学和撞击坑研究.
  • 放射测年法和地质年代学.
  • 行星科学和地球月球系统的演变.

背景情况:

  • 月球球是由石撞击月球而形成的玻璃珠.
  • 阿尔贡-阿尔贡 (40Ar/39Ar) 异位计时技术确定了这些撞击事件的日期.
  • 了解月球撞击历史,可以了解太阳系的演变.

研究的目的:

  • 为了分析阿波罗14号土壤上的月球球体的年龄分布.
  • 为了重建过去35亿年月球石坑形成的速度.
  • 调查月球撞击历史与地球生物进化之间的潜在相关性.

主要方法:

  • 从1克阿波罗14号 regolith中分离出155个月球球.
  • 使用阿尔贡-阿尔贡 (40Ar/39Ar) 离合计技术测定球状球体的年代.
  • 对撞击年龄的统计分析,以确定石坑速率的变化.

主要成果:

  • 在过去的35亿年里,月球石坑的形成速度下降了2-3倍.
  • 在5亿至6亿年前观察到最小的石坑形成率.
  • 在过去的4亿年里,火山口的形成速度增加了3.7±1.2倍.

结论:

  • 月球撞击流没有保持不变,显示出显著的波动.
  • 最近月球撞击的增加恰逢地球上快速进化的辐射时期.
  • 需要进一步的研究来确定月球撞击和陆地生物变化之间的因果关系.