Constrained objects are those that have restrictions on their position, motion, or both. If the machine’s components come into contact with one another, they will create a pair.
If the motion between the two is entirely or partially limited, the pair is referred to as a kinematic pair. The term “constraints” in physics describes the restrictions imposed on an object’s position, movement, or both.
A pair is created when two machine components interact by touching one another. This pair is referred to be a kinematic pair if there is either complete or partial restriction on their movement.
Well, in this reading, we’ll explore what a constrained motion is, its types, examples, diagrams, and its difference from free motion.
Let’s begin
What is Constrained Motion?
Constrained motion is the movement that takes place when the body is free to move in one direction but restricted in all other directions.
When the body is unrestrained, it possesses six degrees of freedom. If all of the degrees of freedom are locked, the body will not move in any direction.
The object travels in a limited manner when it is in a confined motion. The fan’s circular motion, for instance, is a constrained motion.
The constrained force is the force that the constraining object applies to a specific item in order to force it to comply with the movement’s restrictions.
Some examples of constrained motion include:
- A particle travelling over an inclined plane, whether smooth or rough,
- A particle moving gravitationally down a curve,
- A string with a particle attached at one end that is forced to travel in a particular direction.
The best example is riding a bicycle. The relationship created as a result of cycling is the input there. A back wheel’s rotation is the output. - Let’s say we want a car to drive in a straight direction, but it’s travelling in a curved path. We can control it to move it in a straight line with force. One type of constrained motion is straight-line motion.
- The motion of a square bar in a square hole
- The motion of a shaft with a collar at each end in a circular hole,
- A piston in the cylinder of an IC engine.
Related:
Types of Constrained Motion
The three types of constrained motion include:
- Completely constrained motion
- Incompletely constrained motion
- Partially or successfully constrained motion
Completely constrained motion
Completely constrained motion occurs when the pair’s motion is restricted to a single direction Regardless of the direction of the applied force.
A good example of a completely constrained motion would be a rectangular shaft travelling in a single direction through a rectangular hole. There is no other way for the shaft to travel or revolve.
In a steam engine, for instance, the piston and cylinder form a pair, and the piston’s motion is restricted to a single direction; that is, it will only reciprocate in relation to the cylinder, regardless of the crank’s direction of motion.
Incompletely constrained motion
A circular shaft travelling in a circular hole is an example of an incompletely confined motion, where the motion between the pair can occur in more than one direction.
These movements are referred to as incompletely restricted when there are several directions in which a couple can go. The direction of relative motion between the two can be altered by a change in the direction of the impacted force.
Because it may either slide or spin in a hole, a circular shaft or strip in a circular hole is an example of an imperfect restricted motion. There is no relationship between the two movements.
Motions that are not fully constrained include: the circular shaft may either slide or revolve in a round hole.
Partially or successfully constrained motion
Motion in partially constrained motion is limited to one direction when an external force is applied, but it can move in several directions when no external force is applied.
On the other hand, the shaft is prevented from moving axially upward when a load is given to it. Successfully constrained motion is the term used to describe the pair movement.
Successfully constrained motion is another name for partially constrained motion. The footstep bearing is an example of partially constrained motion, as it only travels in one direction when an external force is applied.
Successfully constrained motions include the piston reciprocating inside an engine cylinder and the motion of an I.C. engine valve, which is held in place by a spring. The piston reciprocating inside an engine cylinder
Shaft in a footstep bearing.
What is the difference between free motion and constraint motion?
Free motion is a motion without any restriction (constraint). It is considered unconstrained motion, for example, the motion of a pendulum or the motion of a freely falling body.
When any constraint, any restriction on the motion of a body, is applied, then it is considered constrained motion. For example, rolling a disc on the inclined plane without slipping, and the motion of a ball, which is restricted to moving within the cone.
Conclusion
Constraints are restrictions on an object’s motion, position, or both, due to external forces. These forces keep the motion in check, causing constrained motion.
The elements of a machine, called pairs, are in contact with each other. Constrained motion occurs when a pair’s movement is only along one direction, irrespective of external forces.
This is called ‘completely constrained motion.’. If the motion is only under external forces, it’s known as ‘partially or successfully constrained motion.’ If the motion can occur in more than one direction, it’s called ‘incompletely constrained motion.’
FAQs
What is meant by constrained motion?
Constrained motion is a term that describes a situation where a body is allowed to move in one direction while being restricted in all other directions. This means the object’s motion is limited or constrained. A common example of this is a ceiling fan’s circular motion.
What are the 4 types of constraints in physics?
This is an example of rheonomic, holonomic, dissipative, and unilateral constraint. The forces associated with these restrictions are called forces of constraints or constraint forces.
What is an example of a constraint force?
These forces which constrain the motion are known as ‘constraint forces’. Some examples include the motion of a body on a wedge, a particle sliding down a curve under gravity, a particle tied to one end of a string, the movement of a fan, and many more.
What is the formula for constraint motion?
The restrictions on the motion of any object caused by different factors which reduce its free movement are called constraints. The pulley and constraints relation is given by the equation 2 T P = T + T = 2 T .
