## First Condition

The first condition of equilibrium is the the net force in every directions have to be zero.

You are watching: If only one force acts on an object, can it be in equilibrium?

### Key Takeaways

Key PointsThere room two problems that must be met for an object to be in equilibrium.The an initial condition is the the net force on the object should be zero for the object to be in equilibrium.If net pressure is zero, climate net pressure along any direction is zero.Key Termsforce: A physical amount that denotes ability to push, pull, twisted or accelerate a human body which is measure up in a unit dimensioned in fixed × distance/time² (ML/T²): SI: newton (N); CGS: dyne (dyn)torque: A rotational or twisting result of a force; (SI unit newton-meter or Nm; royal unit foot-pound or ft-lb)translation: movement of a body on a direct path, there is no deformation or rotation, i.e. Such that every component of the human body moves at the very same speed and also in the very same direction; additionally (in physics), the direct motion that a body thought about independently of its rotation.

### First problem of Equilibrium

For an item to it is in in equilibrium, it must be suffering no acceleration. This means that both the network force and the network torque on the object must be zero. Right here we will talk about the very first condition, the of zero network force.

In the form of an equation, this first condition is:

\textF_\textnet = 0.

In stimulate to attain this conditon, the forces acting follow me each axis of movement must sum to zero. For example, the net external forces follow me the typical x– and y-axes space zero. This is written as

\textnet \textF_\textx = 0 and also \textnet \textF_\texty = 0.

The problem \textF_\textnet = 0 have to be true because that both static equilibrium, where the object’s velocity is zero, and dynamic equilibrium, where the object is moving at a constant velocity.

Below, the motionless person is in revolution equilibrium. The pressures acting ~ above him add up to zero. Both forces are upright in this case.

Person in static Equilibrium: This motionless person is in revolution equilibrium.

Below, the car is in dynamic equilibrium since it is moving at constant velocity. There are horizontal and vertical forces, however the net exterior force in any kind of direction is zero. The used force between the tires and the roadway is well balanced by waiting friction, and also the load of the auto is sustained by the regular forces, here shown to be same for all four tires.

A automobile in Dynamic Equilibrium: This vehicle is in dynamic equilibrium due to the fact that it is relocating at continuous velocity. The forces in every directions are balanced.

## Second Condition

The second condition of revolution equilibrium claims that the network torque acting on the object have to be zero.

### Learning Objectives

Identify the 2nd condition of revolution equilibrium

### Key Takeaways

Key PointsThe second condition necessary to accomplish equilibrium entails avoiding sped up rotation.A rotating human body or system can be in equilibrium if its price of rotation is continuous and stays unchanged by the pressures acting ~ above it.The size of torque around a axis of rotation is characterized to it is in τ=rFsinθ.Key Termstorque: A rotational or twisting impact of a force; (SI unit newton-meter or Nm; royal unit foot-pound or ft-lb)equilibrium: The state that a body at remainder or in uniform motion, the result of all forces on which is zero.

A child’s seesaw, shown in, is an instance of revolution equilibrium. An object in static equilibrium is one that has actually no acceleration in any direction. While there might be motion, such movement is constant.

Two children on a seesaw: The device is in revolution equilibrium, reflecting no acceleration in any kind of direction.

If a given object is in static equilibrium, both the network force and also the net torque on the object have to be zero. Let’s break this down:

### Net force Must be Zero

The net force acting top top the object should be zero. Because of this all forces balance in every direction. Because that example, a auto moving along a highway in ~ a consistent speed is in equilibrium, together it is not increasing in any kind of forward or vertical direction. Mathematically, this is proclaimed as Fnet = ma = 0.

### Net Torque have to Be Zero

The 2nd condition necessary to attain equilibrium involves avoiding accelerated rotation (maintaining a constant angular velocity ). A rotating human body or system have the right to be in equilibrium if its price of rotation is constant and stays unchanged through the pressures acting ~ above it.

To recognize what factors influence rotation, let us think around what happens when you open an plain door by rotating it on that hinges.The magnitude, direction, and suggest of applications of the force are integrated into the meaning of the physics quantity referred to as torque—the rotational identical of a force. It is a measure of the effectiveness of a pressure in changing or accelerating a rotation (changing the angular velocity over a period of time).

In equation form, the magnitude of torque is identified to be τ=rFsinθ wherein τ (the Greek letter tau) is the symbol because that torque, r is the street from the pivot suggest to the point where the pressure is applied, F is the size of the force, and θ is the angle between the force and also the vector command from the suggest of applications to the pivot point.

## Two-Component Forces

In equilibrium, the network force and also torque in any details direction equal zero.

### Learning Objectives

Calculate the net force and the net torque for things in equilibrium

### Key Takeaways

Key PointsIn equilibrium, the net force in all directions is zero.If the net minute of inertia around an axis is zero, the object will have no rotational acceleration around the axis.In every direction, the net pressure takes the form: \sum \textbfF=\textm\textbfa=0 and also the network torque take the form: \sum \boldsymbol\tau=\textI\boldsymbol\alpha=0 whereby the amount represents the vector sum of all forces and also torques acting.Key Termsequilibrium: The state the a human body at rest or in uniform motion, the resultant of all pressures on i beg your pardon is zero.

An object with consistent velocity has actually zero acceleration. A motionless object still has consistent (zero) velocity, so motionless objects likewise have zero acceleration. Newton’s second law claims that:

\sum \textbfF=\textm\textbfa

so objects with continuous velocity likewise have zero net outside force. This way that all the pressures acting on the thing are well balanced — the is to say, they are in equilibrium.

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This rule likewise applies to activity in a certain direction. Consider an item moving along the x-axis. If no net pressure is applied to the object follow me the x-axis, the will continue to relocate along the x-axis at a continuous velocity, through no acceleration.

Car moving at consistent Velocity: A moving automobile for i m sorry the net x and y force contents are zero

We can easily extend this rule to the y-axis. In any type of system, uneven the used forces publication each other out (i.e., the resultant pressure is zero), there will certainly be acceleration in the direction the the result force. In revolution systems, in which movement does no occur, the sum of the forces in all directions always equals zero. This concept can be stood for mathematically v the complying with equations:

\sum \textF_\textx=\textma_\textx=0

\sum \textF_\texty=\textma_\texty=0

This rule additionally applies come rotational motion. If the result moment around a certain axis is zero, the thing will have no rotational acceleration around the axis. If the object is no spinning, it will certainly not start to spin. If the object is spinning, the will continue to spin in ~ the same consistent angular velocity. Again, we can extend this come moments about the y-axis together well. We can represent this preeminence mathematically with the complying with equations: