Name: gravity and work on sloped motion
Uploaded: 2023-05-16T08:18:40.000Z
Duration: 1 min 11 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

Energy

PS.PSc.7.3

Work Done Over an Inclined Plane

Pensemos en una persona que esquía por una pendiente. Suponiendo que la fuerza debida a la fricción sobre los esquís es insignificante sobre el hielo, se puede dibujar un diagrama de cuerpo libre.
El componente de la fuerza gravitacional a lo largo del desplazamiento mueve a la persona hacia adelante. Las fuerzas perpendiculares al desplazamiento no tienen ningún papel en el movimiento y, por lo tanto, no contribuyen al trabajo realizado.
Por lo tanto, el trabajo realizado es simplemente el componente de fuerza paralela multiplicado por el desplazamiento.
Otra forma de resolver esto es tomando el vector de fuerza en lugar de su componente. 
Aquí, se considera el ángulo entre la fuerza y el desplazamiento. Tenga en cuenta que la expresión final para el trabajo realizado es la misma.
Sin embargo, si el desplazamiento del esquiador es en la dirección opuesta a la fuerza, de modo que comienza y termina en reposo, entonces el trabajo realizado es negativo.
Si el ángulo del plano inclinado es cero, la fuerza es perpendicular al desplazamiento, por lo que el trabajo realizado por la fuerza gravitacional sobre la persona se vuelve cero.

<ol>
	<li>Halliday, Resnick y Walker (2014), Fundamentos de Física, 10ª edición, Wiley and Sons Inc.: sección 7.3; páginas 156-157.</li>
</ol>

trabajo realizado sobre un plano inclinado

El marco del centro de masa ayuda a describir fácilmente el trabajo realizado en cuerpos rígidos. Dado que las fuerzas internas en un cuerpo rígido no realizan trabajo, pueden ser ignoradas y las fuerzas externas pueden ser consideradas en el teorema de energía-trabajo. El trabajo realizado por la gravedad para mover un cuerpo rígido, o el trabajo realizado por una fuerza opuesta para mover un cuerpo rígido en contra de la gravedad, se puede calcular utilizando el marco del centro de masa. Es la integral de línea de la fuerza de gravedad sobre la trayectoria, considerada positiva si la gravedad aumenta su energía cinética y negativa si se realiza trabajo en contra de la gravedad para levantarlo, reduciendo así su energía cinética. En el caso del movimiento horizontal, el trabajo realizado por o en contra de la gravedad es cero. Es decir, el cambio en la energía cinética de un cuerpo, incluso si no es cero, es puramente debido a otras fuerzas. La formulación es igualmente válida cuando un cuerpo se mueve sobre un plano inclinado. La única diferencia es que solo una componente de la gravedad está a lo largo del plano y solo esta componente debe ser considerada al calcular el trabajo realizado. La fuerza gravitacional perpendicular al plano no realiza trabajo en ningún punto durante el desplazamiento.

Trabajo Realizado sobre un Plano Inclinado

El marco del centro de masa ayuda a describir fácilmente el trabajo realizado en cuerpos rígidos. Dado que las fuerzas internas en un cuerpo rígido no funcionan, pueden ser ...

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Education

Educación

JoVE Core

Physics

Física

Unit 1

Unidad 1

Work and Kinetic Energy

Trabajo y Energía Cinética

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

gravity and work on sloped motion

Gravity and work on sloped motion can be described with the center-of-mass framework. For a rigid body, internal forces do no work, so they can be ignored. The work-energy theorem then uses only the external forces.

The work done by gravity depends on the path of the body’s center of mass. If gravity helps increase kinetic energy, the work is positive. If an object is lifted against gravity, the work is negative because kinetic energy decreases.

For horizontal motion, the work done by or against gravity is zero. In that case, any change in kinetic energy comes from other forces. The same idea applies to motion over an inclined plane.

On a slope, only the component of gravity parallel to the plane contributes to work. The force perpendicular to the plane does no work during the motion. That is the key difference from horizontal motion and other straight paths.

Gravity and Work on Sloped Motion

work

Work in Physics: Force and Motion

Work in physics connects force, motion, and energy transfer. Work is done when a force acts on an object and that object moves from one position to another. If there is no displacement, no work is done, even if a force is present. The amount of work depends on the force and the direction of motion. For a very small displacement, the work done is written as the dot product of force and displacement vectors. That means work depends on the size of the vectors and the angle between them. You can...

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Work in physics depends on the direction of a force and the way an object moves. Work is done when energy is transferred to an object. It happens when a force acts on a body that moves from one position to another. The work done by a force is defined as the integral of the force with respect to displacement along the path. Forces can change with position, and an object can move along different paths between the same two points. In vector form, the size of a force times the cosine of the angle...

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Kinetic energy depends on an object’s mass and speed. A heavier object moving at the same speed has more kinetic energy than a lighter one. An object moving faster also has more kinetic energy when the mass stays the same. The transcript also describes several forms of kinetic energy. Mechanical energy is linked to the motion of an object. A bullet fired from a gun and water flowing down a dam are examples of mechanical energy. Electrical energy comes from the flow of electric charges.

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Motion Energy in Collisions

Kinetic energy is the energy of motion. It depends on how fast an object moves, not on the direction of its velocity. In classical mechanics, this idea helps explain how moving bodies affect other bodies during collisions. A classic example is a perfectly elastic, head-on collision between two identical bodies, with one body initially at rest. After the collision, the first body stops, and the second body moves away with the first body's original velocity. This same pattern can be seen in...

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Kinetic Energy, Momentum, and Reference Frames

Kinetic energy depends on mass, speed, momentum, and the frame of reference. For a particle, it is one-half of the particle’s mass times the square of its speed. The same idea can also be written in terms of mass and momentum instead of mass and velocity. The units of kinetic energy are mass times speed-squared. These units match the units of work. Force times distance also gives the same units, so kinetic energy and work are measured in joules. That is why work and kinetic energy are two...

work-energy theorem

Work Done and Kinetic Energy

Work done by the net force is linked to an object's kinetic energy. In physics, the net force is the total force acting on an object. Kinetic energy is the energy of motion. The work-energy theorem states that the work done by all forces on an object equals the change in its kinetic energy. This relationship is useful when acceleration is not constant. If the change in velocity is known, the theorem can still help calculate the work done by a force. It connects force, motion, and energy in a...

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Variable Force Work via Graphs and Energy

Variable force work and energy can be found by using force-displacement graphs and the work-energy principle. When a force changes as an object moves, the calculation is more complex than for a constant force. Work is the product of force and displacement, and energy is the capacity of a system to do work. For a constant force, work is found by multiplying the force by the distance moved in the direction of the force. For a variable force, the work done is the area under the force-displacement...

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work-energy theorem for motion along a curve

work-energy-theorem-for-motion-along-a-curve

Work-Energy Along Curved Paths

The work-energy theorem can be applied to motion along a curved path. A curved path can be treated as many tiny straight paths added together. On each small part, the force can be taken as constant, so the work-energy theorem can be used there. The total result comes from adding the work done along all of those small path segments. The net work is found with an integral, which adds the work from each infinitesimal path. The total change in kinetic energy is the sum of the changes along the way.

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work done over an inclined plane

Gravity and work on sloped motion can be described with the center-of-mass framework. For a rigid body, internal forces do no work, so they can be ignored. The work-energy theorem then uses only the external forces. The work done by gravity depends on the path of the body’s center of mass. If gravity helps increase kinetic energy, the work is positive. If an object is lifted against gravity, the work is negative because kinetic energy decreases. For horizontal motion, the work done by or...

work done by many forces

Calculating Work from Multiple Forces

Calculating work from multiple forces can be done in two ways, and both methods give the same result. One method finds the work done by each force first. The other method finds the net force by adding the force vectors first.

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Gravity and Positive vs Negative Work

Gravity is one of the four fundamental forces in nature. On Earth, the force between an object and Earth is called gravity. Gravity does work on an object when it moves the object toward Earth’s center. In that case, the work done by gravity is positive. When an external force lifts an object away from Earth’s center, that force works against gravity. The net work done in this case is negative. If an object moves along the Earth with no change in distance toward or away from Earth’s center,...

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power

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Power connects work with the time needed to do it. Work depends on force and displacement. The work-energy theorem also links net work on an object to the change in its kinetic energy between two points on its path. These ideas do not include time directly, but time still matters in many real situations. A sprinter is a clear example. Two runners may reach the same finish speed, so they do the same amount of work. The winner is the one who reaches that speed in less time. Power describes this...

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Power describes how fast work is done. In physics, two sprinters can cross the finish line with the same velocity and do the same amount of work, but the one who finishes first has greater power because the work takes less time. Average power is the work done during a time interval divided by that time interval. When the time interval becomes very small, this becomes instantaneous power. That gives the power at a specific moment instead of over a longer stretch of time. Power can also be...

key terms and concepts

Learn how gravity does work on a rigid body moving over an inclined plane, why only the parallel force matters, and when gravity does no work.

Gravity and Work on Sloped Motion | JoVE K12

physics

JoVE Core Física presenta la teoría y la aplicación de conceptos físicos fundamentales, como la cinemática, dinámica, mecánica de fluidos, estática, ondas y acústica, mediante animaciones audiovisuales concisas y fáciles de entender. Además, los vídeos de científicos en acción muestran la aplicación de los conceptos relacionados en experimentos de investigación clásicos y originales, realizados en laboratorios de todo el mundo.

PS.Phy.6.2

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Forces, Momentum And Motion

Forces in two dimensions

Tennessee Academic Standards

High School

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

PHYS.PS2.4

PHYS.PS3.6

Alabama Course of Study Science

9-12.P.2.3.b

9-12.P.2.3.c

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PS.PSc.7.1

The universe is composed of matter in different forms, and all forms of matter contain energy.&#160; The different forms of energy on Earth originate from ...

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PS.PSc.7.2

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When an object is acted upon by a variable force, the amount of work done and the change in energy of the object can be more complex to calculate compared ...

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The work-energy theorem can be generalized to the motion of a particle along any curved path. The simple argument here is that the curved path can be ...

The center-of-mass framework helps to easily describe the work done on rigid bodies. Since the internal forces in a rigid body do no work, they can be ...

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Power

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PS.PSc.7.4

Analyze energy transfers and transformations within a mechanical system.

Gravity and Work on Sloped Motion

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