Name: free-fall acceleration on earth
Uploaded: 2023-09-22T11:49:39.000Z
Duration: 55 s
Channel: JoVE

设想一位女士在移动时推动一辆行李车。她施加的外力使行李车沿着力的方向加速运动。
如果她施加更大的力，小车会移动得更快。要使小车停下，她需要在与运动方向相反的方向施加一个外力。
如果她在小车上放置更多的行李，相同的力在合外力方向上产生的加速度会更小。
综合以上内容，我们得到牛顿运动第二定律，该定律指出：物体的加速度与合外力成正比，方向与合外力方向相同，且与物体质量成反比。
或者，作用在物体上的合外力等于其质量与加速度的乘积。&#160;所有加速运动的物体都遵循牛顿第二定律。

地球上重力引起的加速度

牛顿第二定律与他的第一运动定律密切相关。 它以数学形式揭示了力和运动变化之间的因果关系。 牛顿第二定律是定量的，广泛用于计算在受到外力作用时物体的运动变化。 作用在一个系统上的所有外力相加，产生净外力Fnet。 净外力越大，产生的加速度越大。 该加速度与作用在系统上的净外力成正比且方向相同。 此外，考虑到惯性，加速度应与系统质量成反比。 换句话说，质量（即惯性）越大，给定外力产生的加速度越小。 实验表明，加速度与质量完全成反比，正如它与净外力成正比一样。 也就是说，物体的加速度仅取决于所受净外力和质量。 将这两个比例结合起来就得出了牛顿第二定律，该定律指出：系统的加速度与作用在系统上的净外力成正比且方向相同，同时与其质量成反比。 第二定律描述了物体如何对外部环境做出机械响应。 外部环境的影响是合力，物体的响应表现为加速度，响应的强度与质量成反比。 牛顿还用动量概述了他的第二定律：物体动量的瞬时变化率等于作用在物体上的净外力。 本文改编自 <a href="https://openstax.org/books/university-physics-volume-1/pages/5-3-newtons-second-law">Openstax，《大学物理》第 1 卷，第 5.3 节：牛顿第二定律。</a>

牛顿第二定律与他的第一运动定律密切相关。它从数学上给出了力与物体运动状态变化之间的因果关系……

Education

教育

JoVE Core

Mechanical Engineering

机械工程

Unit 1

第一单元

Physics Basics

物理基础

KEY TERMS AND CONCEPTS

关键术语与概念

Acceleration due to Gravity on Earth

free-fall acceleration on earth

Free-fall acceleration on Earth describes how fast an object speeds up when gravity is the only force acting on it. Near Earth’s surface, this acceleration is nearly constant for many everyday situations.

Gravity pulls objects toward Earth and gives them downward acceleration. This motion is often written as g, and it helps explain why falling objects gain speed as they move downward.

The value of g is commonly used in physics to predict the motion of objects dropped or released near the ground. It is an important idea for understanding motion on Earth and for solving basic mechanics problems.

Free-Fall Acceleration on Earth

introduction to scalers

Scalar Quantities in Physics

Scalar quantities in physics have size only. They do not include direction. This makes them different from vector quantities. Common scalar examples include mass, temperature, time, and energy. Each one can be described with a number and a unit. Because direction is not part of the value, scalars are often easier to compare and measure.

vector or cross product

Cross Product of Two Vectors

The cross product of two vectors gives a new vector that is related to both original vectors. It is also called the vector product. In many physics problems, this operation helps describe quantities that depend on direction as well as size. The result of a cross product has a direction set by the two input vectors. It is not the same as ordinary multiplication. The transcript focuses on the vector or cross product as a core vector operation students use when working with vectors in science.

introduction to vectors

Vectors in Motion and Direction

Vectors describe quantities that have both size and direction. They are used in physics to show how motion, force, and other quantities act in space. A vector can be represented with an arrow. The length of the arrow shows the size, and the arrowhead shows the direction. This makes vectors useful for comparing how one quantity points relative to another. Scalars are different because they have size only and no direction. Understanding the difference between vectors and scalars is an important...

units and standards of measurement

Measurement Units, Standards, and SI Basics

Measurement units, standards, and SI basics help scientists describe physical quantities clearly. A unit gives a number meaning, while a standard provides a fixed reference for that measurement. Together, they make results easier to compare and understand. The International System of Units, or SI, is the most common measurement system in science. It uses agreed-upon base units for common quantities. These standards reduce confusion when measurements are shared across labs, classrooms, and...

accuracy and precision

Measurement Errors, Accuracy, and Precision

Measurement errors can affect how close a result is to the true value and how consistent repeated results are. Accuracy describes how close a measurement is to the accepted or true value. Precision describes how close repeated measurements are to one another. A result can be accurate, precise, both, or neither. A set of measurements may cluster tightly together and still be far from the true value. Another set may include values spread out from one another, even if one of them is close to the...

rules of significant figures

Counting Significant Figures in Measurements

Significant figures help students record measurements with the correct level of precision. They show which digits in a number are meaningful and which only help place the decimal point. In science class, this idea matters when writing and comparing measured values. The rules for significant figures explain how to count these digits in different numbers. Some digits are always counted, while others depend on where they appear in the number. Learning the rules makes it easier to report answers...

random and systematic errors

Measuring Error in Scientific Data

Random and systematic errors affect scientific measurements. Random errors cause values to spread around the true value. They make repeated measurements less consistent. Systematic errors shift measurements in the same direction each time. Understanding both kinds of error helps students judge data quality. Random error can come from small changes during measurement. Systematic error can come from a biased tool or method. Scientists look for these patterns so they can improve results and...

position and displacement

Tracking Motion with Position and Displacement

Position and displacement are key ideas in straight-line motion. Position tells where an object is located compared with a chosen starting point, called the origin. Displacement describes how far and in what direction the object has moved from its starting position. These ideas help describe motion clearly. Position can change as an object moves. Displacement focuses on the change in position, not just the path taken. That makes it useful for comparing motion in a simple and precise way.

position and displacement vectors

Using Vectors to Describe Motion

Position and displacement vectors describe motion in physics. A position vector shows where an object is located relative to a chosen origin. A displacement vector shows how far and in what direction the object moves from one point to another. These vectors are useful because they give a clear way to track movement in space. The video connects position and displacement to the idea of a reference point and shows how direction matters as much as distance. That makes them important for describing...

mass and weight

How Mass Differs from Weight

Mass and weight are related, but they are not the same. Mass is the amount of matter in an object. Weight is the force of gravity acting on that object. This difference matters because mass stays the same even when gravity changes. Weight can change if the gravitational pull changes. A person or object therefore has the same mass, but not always the same weight. The terms are often used in everyday speech as if they mean the same thing. In physics, they describe two different ideas.

acceleration due to gravity on earth

Free-fall acceleration on Earth describes how fast an object speeds up when gravity is the only force acting on it. Near Earth’s surface, this acceleration is nearly constant for many everyday situations. Gravity pulls objects toward Earth and gives them downward acceleration. This motion is often written as g, and it helps explain why falling objects gain speed as they move downward. The value of g is commonly used in physics to predict the motion of objects dropped or released near the...

tension

Tension in Ropes and Strings

Tension is the pulling force carried by a rope, string, or cable when it is stretched by a load. In physics, this force acts along the length of the object and pulls away from the objects at each end. A stretched rope can support a hanging mass because the tension in the rope balances the weight of the load. The same idea appears in many everyday situations, such as a cable holding a sign or a string lifting an object. Understanding tension helps students connect force diagrams to real motion.

gravitational force

How Gravity Acts Between Objects

Gravity is a force that pulls objects toward one another. On Earth, this force gives objects weight and keeps people, water, and other materials from drifting away. It also helps explain why planets and moons stay in motion around larger bodies. The strength of gravitational force depends on the masses of the objects involved. Larger masses create a stronger pull, while smaller masses create a weaker one. The distance between objects also matters, because gravity becomes weaker as objects move...

key terms and concepts

Learn how free-fall acceleration near Earth works, why gravity makes falling objects speed up, and how g is used in basic physics problems.

Free-Fall Acceleration on Earth | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Free-Fall Acceleration on Earth

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Transcript