Name: force, motion, and mechanical effects
Uploaded: 2023-09-22T11:49:19.000Z
Duration: 1 min 25 s
Channel: JoVE

Lorsqu’un homme tire ou pousse une boîte, celle-ci se déplace dans une direction horizontale. La traction ou la poussée exercée sur la boîte qui entraîne son mouvement est connue sous le nom de force. Il s’agit d’une quantité vectorielle exprimée en newton.
Les forces agissant sur les corps peuvent être classées en forces externes et internes. Lorsque la force appliquée à l’extérieur sur un corps crée un effet, on parle de force externe, tandis que les forces de réaction existant à l’intérieur du corps sont appelées forces internes.
Le principe de transmissibilité stipule que si le point d’application d’une force sur un corps change mais reste dans la même ligne d’action, la force résultante sur le corps ne change pas.
Considérons deux forces agissant sur un corps rigide. Selon le principe de transmissibilité, le corps reste inchangé si les forces agissant sur le corps sont dans la même ligne d’action, même lorsqu’elles agissent en différents points.
Comme ces forces sont égales et opposées, leur somme est égale à zéro, et la force résultante sur le corps reste inchangée.

<ol>
	<li>Meriam, J.L., Kraige, L.G., Bolton, J.N. (2018). Génie mécanique \u2012 Statique, New Jersey : John Wiley & Sons. pp – 23-24.</li>
	<li>Bière, F.P. ; Johnston, E.R. ; Mazurek, D.F ; Cromwell, P.J. et Self, B.P. (2019). Mécanique vectorielle pour les ingénieurs \u2012 Statique et dynamique. New York : McGraw-Hill. pp 85 à 86.</li>
</ol>

introduction à la forcet

Considérons l'eau qui s'écoule d'une buse vers une aube de turbine. Lorsque l'eau frappe l'aube de la turbine, elle exerce une force qui la fait avancer dans la direction de l'écoulement. La force est une force qui modifie le mouvement, la forme ou l'orientation d'un objet. Les forces peuvent être provoquées par un contact physique, tel qu'une poussée ou une traction, ou par des interactions non-physiques, telles que des forces magnétiques ou gravitationnelles. La force est une quantité vectorielle avec à la fois une magnitude et une direction, et elle est mesurée en newtons (N) dans le système d'unités SI. Considérons un objet d'une masse de 1 kg qui se déplace vers l'avant avec une accélération de 1 m/s². Dans ce cas, la force appliquée sur l'objet équivaut à 1 N. En mécanique, les forces externes et internes sont deux types de forces qui agissent sur un corps rigide en considération, ce qui entraîne des effets externes et internes. Les effets externes sont les forces réactives que le corps exerce sur son environnement en raison de forces externes telles que le poids du corps, les forces appliquées par les personnes et les forces de friction. Les effets internes sont les forces internes et les déformations qui se produisent à l'intérieur du matériau du corps. Considérons un exemple d'une équerre soumise à une force externe. Les effets externes de cette force sur l'équerre sont les forces réactives que la fondation et les boulons exercent sur l'équerre. Les effets internes de la force sur l'équerre sont les contraintes internes résultantes et les déformations qui se produisent à l'intérieur du matériau de l'équerre. Ces forces internes et déformations sont réparties dans tout le matériau de l'équerre et dépendent des propriétés du matériau et des géométries du corps. Le principe de transmissibilité est un concept qui explique les effets de déplacement du point d'application d'une force appliquée le long de la même ligne d'action. Il indique que, si une force est appliquée à un corps rigide et que le point d'application de cette force change tout en restant sur la même ligne d'action, la force résultante agissant sur le corps restera inchangée. Considérons deux forces égales agissant sur un corps rigide à partir de différents points. Selon le principe de transmissibilité, les forces agissant sur le corps sont sur la même ligne d'action, ce qui les rend équivalentes à une seule force agissant en un point particulier. Lorsque le point d'application de ces forces est modifié ou déplacé le long de la même ligne d'action, la force résultante sur le corps reste la même, car c'est la même force agissante sur la même ligne d'action.

Introduction à la forceT

Considérez l’eau qui s’écoule d’une buse à une aube de turbine. Lorsque l’eau frappe l’aube de la turbine, elle exerce une force qui la fait se déplacer le long de l’écoulement de ...

Education

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Mechanical Engineering

Génie mécanique

Unit 1

Unité 1

Force Vectors

Vecteurs de force

KEY TERMS AND CONCEPTS

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Introduction to force

force, motion, and mechanical effects

Force changes the motion, shape, or orientation of an object. A flowing stream of water can push on a turbine vane and make it move in the direction of the flow. In mechanics, force is treated as a vector quantity, which means it has both magnitude and direction. It is measured in newtons, or N, in the SI unit system.

Forces can act through direct contact or without contact. A push or pull is a contact force. Magnetic and gravitational forces are examples of non-contact interactions. For an object with a mass of 1 kg that accelerates at 1 m/s2, the applied force is 1 N.

When a rigid body is under load, mechanics separates the effects into external forces and internal forces. External forces produce the reactive forces that the body exerts on its surroundings. These can include body weight, forces applied by people, and frictional forces. Internal effects are the stresses and deformations that develop inside the material.

A bracket loaded by an external force shows both kinds of effects. The foundation and bolts react to the force on the bracket. At the same time, internal stresses and deformations spread through the bracket material. These internal forces depend on the material properties and the shape of the body.

The principle of transmissibility explains what happens when the point of application of a force moves along the same line of action. If the force stays on that line, the resultant force on a rigid body does not change. Two equal forces on a rigid body can therefore be treated as a single equivalent force when they act along the same line of action.

Force, Motion, and Mechanical Effects

scalar and vectors

Scalar vs Vector Quantities in Mechanics

Scalar and vector quantities are two main ways to describe physical quantities in mechanics. Common examples include force, speed, velocity, and work. Some of these are scalars, and others are vectors. A scalar is a quantity that has magnitude only. It does not need direction. Mass, area, and length are examples of scalar quantities. Scalars with the same units can be added or subtracted like ordinary numbers. A class that ends 10 min earlier than 50 min lasts 50 min minus 10 min, which is 40...

vector operations

Adding and Multiplying Vectors

Vectors are quantities with both magnitude and direction, and their operations include addition, subtraction, and scalar multiplication. Scalar multiplication means a vector is multiplied by a scalar value, which creates a new vector with a different magnitude. If the scalar is positive, the direction stays the same. If the scalar is negative, the direction reverses. A common example is momentum, which comes from multiplying mass by velocity. In this case, mass is the scalar quantity and...

introduction to force

Force changes the motion, shape, or orientation of an object. A flowing stream of water can push on a turbine vane and make it move in the direction of the flow. In mechanics, force is treated as a vector quantity, which means it has both magnitude and direction. It is measured in newtons, or N, in the SI unit system. Forces can act through direct contact or without contact. A push or pull is a contact force. Magnetic and gravitational forces are examples of non-contact interactions. For an...

force classification

Types of Forces in Physics

Forces in physics can be grouped by how they act and where they come from. These groups help describe motion, behavior, and equilibrium in the physical world. They are also useful in physics and engineering. One common way to classify forces is by whether they need contact. Contact forces act only when two objects touch. Frictional force, tension, and normal force are all contact forces that come from surface contact. Forces can also act without physical touch. These are called non-contact...

vector addition of forces

Resultant Force from Tugboats

Resultant force can be found with vector addition when two or more forces act on the same object. This idea helps explain how multiple pulls combine to create one net force. It is a key tool for understanding motion in physics. A clear example is a ship pulled by two small tugboats. The forces, F1 and F2, act at the same time but in different directions. The net force on the ship is the vector sum of those two forces. The parallelogram law gives a geometric way to add vectors. In this method,...

two-dimensional force system

Resolving Forces in a Plane

Resolving forces in a plane is a key part of two-dimensional mechanical analysis. A force vector can be split into x- and y-components, which show how the force acts in each direction. These components are written with the help of unit vectors, one for the x direction and one for the y direction. To find the components in a Cartesian coordinate system, first identify the angle theta between the force and the positive x-axis. If the line of action passes through the origin, basic trigonometry...

two-dimensional force system: problem solving

two-dimensional-force-system-problem-solving

Two-Dimensional Forces: Free-Body Analysis

Two-dimensional force analysis starts with a free-body diagram. A free-body diagram shows the object and every external force acting on it. It includes each force’s size, direction, and point of application. After the diagram is drawn, each force is broken into x- and y-components. This uses vector analysis and trigonometry, especially sine and cosine. The forces can then be written in Cartesian vector form, which makes them easier to work with. Next, the components in each direction are...

scalar notation

Vector Components for Force Calculations

Scalar notation helps simplify vector calculations by breaking a vector into separate x and y parts. When vectors are added or subtracted, each component can be handled on its own using scalar notation. This makes force problems easier to solve.

cartesian vector notation

Vector Components in 3D Space

Cartesian vector notation shows how to write vectors in three-dimensional space using x, y, and z components. It gives a clear way to represent direction and size for quantities used in mechanical engineering. The notation uses the unit vectors i, j, and k for the x, y, and z axes. A vector pointing in the direction (3, −4, 5) can be written as A = 3i - 4j + 5k. The unit vectors are i = (1, 0, 0), j = (0, 1, 0), and k = (0, 0, 1). This form is useful for describing displacement, velocity,...

direction cosines of a vector

Vector Orientation with Direction Cosines

Direction cosines describe how a vector is oriented relative to the x, y, and z axes. For a vector A written in Cartesian form with i, j, and k unit vectors, this idea helps connect the vector’s components to its direction in space. The magnitude of vector A is the square root of the sum of the squares of its components. Its direction is described by the coordinate direction angles α, β, and γ with the x, y, and z axes. These angles can be found by projecting vector A onto each axis. The...

three-dimensional force system

Force Components in 3D Space

A three-dimensional force system describes forces acting in x, y, and z directions. In mechanical engineering, this framework helps students and engineers study how objects and structures behave in three-dimensional space. One common example is a force acting on a particle in space. That force can be split into three parts: the x-component, the y-component, and the z-component. Vector mathematics is used to calculate each component, and together they make up the full three-dimensional force...

three-dimensional force system:problem solving

three-dimensional-force-systemproblem-solving

Resolving Forces in 3D Coordinates

Three-dimensional force systems involve forces acting in three different directions at the same time. These problems are common in physics and engineering. They are used to find the resultant force, which helps predict or analyze how an object or structure will behave. The first step is to resolve each force into scalar components. A scalar component is the amount of force along one axis. Trigonometric functions and vector addition are used to break the force into parts and then combine those...

position vectors

Using Position Vectors to Locate Points

Position vectors are used to locate points in space and show the direction and distance between two points. In math and science, they help describe spatial relationships and make calculations easier. A position vector can connect one point to another point or show a point’s location relative to the origin of coordinates. For a point P(x, y, z) relative to the origin O, the position vector r runs from O to P. In Cartesian vector form, it is written as r = x i + y j + z k. Here, i, j, and k are...

force vector along a line

Finding a Cable Force from Two Points

A cable force can be found from the two points that define its line of action. In three-dimensional statics, this setup often appears with a pole and a cable anchored to the ground. The cable ends are labeled A and B, and their position vectors are written as P_A and P_B. The position vector from A to B is found using the triangle law of vector addition. First, subtract P_A from P_B to get P_AB. Then find the magnitude of P_AB by taking the square root of the sum of the squares of its...

dot product

Using Dot Product to Find Work and Angle

The dot product connects vectors, work, and direction in mathematics and physics. In engineering, it is found by multiplying the magnitudes of two vectors and the cosine of the angle between them. It is shown with a dot symbol between the vectors. A real-world example is a vehicle pulling an object along the ground with a rope. If the rope is angled above the horizontal axis, the work done can be calculated with the dot product of the applied force and the object’s displacement. This makes the...

dot product: problem solving

Using the Dot Product to Solve Vector Questions

The dot product helps solve vector questions by combining vector size and the cosine of the angle between them. It is useful when the angle is measured anti-clockwise and when a problem asks for a vector relationship in component form. A good first step is to identify the question being asked. Then list the given vectors and write them in Cartesian form, also called component form. This makes the data easier to use in a calculation. Next, decide whether the dot product is the right operation.

cross product

Cross Product Direction and Magnitude

The cross product is a vector operation in vector algebra that creates a third vector from two input vectors. Unlike the scalar product, it does not give a single number. The result is a vector perpendicular to both original vectors. The size, or magnitude, of the cross product depends on the magnitudes of both vectors and the sine of the angle between them. A larger angle between the vectors gives a larger cross product magnitude. The direction is found with the right-hand rule. If the...

key terms and concepts

Learn how force changes motion, shape, and orientation, plus the difference between contact and non-contact forces, internal effects, and transmissibility.

Force, Motion, and Mechanical Effects | 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

Force, Motion, and Mechanical Effects

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