Example
Balanced and unbalanced forces
When an object is in equilibrium, that is, it is not moving with changing speed, the net force acting on it is balanced.
For example, when an apple hangs from a tree, the weight of the apple is balanced by the force exerted by the branch on the apple.
When an object is moving with changing speed, the net force on it is unbalanced.
For example, when an apple falls from the tree an unbalanced force equal to its weight is acting on the apple.
For example, when an apple hangs from a tree, the weight of the apple is balanced by the force exerted by the branch on the apple.
When an object is moving with changing speed, the net force on it is unbalanced.
For example, when an apple falls from the tree an unbalanced force equal to its weight is acting on the apple.
Definition
FBD for a single object with multiple forces acting on it
Law
Galileo's law of inertia
Before Galileo developed the concept of Inertia, people believed that a push was necessary to keep something moving.
Galileo, first of all, said that that object moves with constant speed when no forces act on them.
This means that if an object is moving on a frictionless path and no other force is acting upon it, then the object would be moving at that constant speed forever.
But practically it is impossible for any object to attain the condition of zero unbalanced force, as forces like Force of friction, Force of air and many other forces are always acting upon the object.
Later on, Sir Isaac Newton built on Galileo's concept of Inertia to include all objects, giving formation to Newton's First Law of Motion.
Result
Galileo's experiment on motion
Galileo studied motion of objects on an inclined plane in two experiments and leading the same conclusion as follows,
An objects moving down an inclined plane accelerate (i), while those moving up retard (ii) and Motion on a horizontal plane is an intermediate situation(iii).
Galileo concluded that an object moving on a frictionless horizontal plane must neither have acceleration nor retardation, i.e. it should move with constant velocity.
A ball released from rest on one of the planes rolls down and climbs up the other and the final height of the ball is nearly the same as the initial height (a).
If the slope of the second plane is decreased and the experiment repeated, the ball will still reach the same height, but in doing so, it will travel a longer distance(b).
In the limiting case, when the second plane is i.e. is a horizontal the ball travels an infinite distance(c).
Definition
Kinds of Inertia
There are three types of inertia:
1. Inertia of rest: The ability of a body to resist any change in its state of rest. i.e. body at rest.
2. Inertia of motion: The ability of a body to resist any change in its state of motion. i.e. moving body with uniform speed.
3. Inertia of rotation: The ability of a body to resist any change in its state of rotation.i.e. rotating body with uniform speed.
1. Inertia of rest: The ability of a body to resist any change in its state of rest. i.e. body at rest.
2. Inertia of motion: The ability of a body to resist any change in its state of motion. i.e. moving body with uniform speed.
3. Inertia of rotation: The ability of a body to resist any change in its state of rotation.i.e. rotating body with uniform speed.
Definition
Inertia
If the net external force is zero, a body at rest continues to remain at rest and a body in motion continues to move with a uniform velocity. This property of the body is called inertia (i.e. resistance to change).
Definition
Inertia and Mass
The inability of a body to change its state of rest or of uniform motion by itself is called inertia.
Inertia of a body depends mainly upon its mass. If we kick a football, it flies away.But if we kick a stone of the same size with equal force, it hardly moves. Instead, we may injury our foot. A force, that is just enough to cause a small carriage to pick up a large velocity, will produce a negligible change in the motion of a train. We say that the train has more inertia than the carriage.
Clearly, more massive objects offer larger inertia. The inertia of an object is measured by its mass.
Inertia of a body depends mainly upon its mass. If we kick a football, it flies away.But if we kick a stone of the same size with equal force, it hardly moves. Instead, we may injury our foot. A force, that is just enough to cause a small carriage to pick up a large velocity, will produce a negligible change in the motion of a train. We say that the train has more inertia than the carriage.
Clearly, more massive objects offer larger inertia. The inertia of an object is measured by its mass.
Law
First law of motion
A body continues to be in its state of rest or in uniform motion in a straight line unless an external unbalanced force is applied on it.
Definition
Linear Momentum
Linear momentum is defined as a product of mass of an object and its velocity. It's a vector quantity. Any change in mass or the velocity of the system causes change in linear momentum.
Law
Second Law of Motion
The rate of change of momentum of a body is directly proportional to the force applied on it and this change in momentum takes place in the direction of the applied force.
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