Inertia is the property of a body to remain at rest or to remain in motion with constant velocity. Some objects have more inertia than others because the inertia of an object is equivalent to its mass. This is why it is more difficult to change the direction of a boulder than a baseball.
You may have learned it in gradeschool, though. The second law states that the net force on an object is equal to the rate of change, or derivative, of its linear momentum. English scientist Sir Isaac Newton examined the motion of physical objects and systems under various conditions.
In , he published his three laws of motion in Philosophiae Naturalis Principla Mathematica. The laws form the basis for mechanics—they describe the relationship between forces acting on a body, and the motion experienced due to these forces. These three laws state:. The first law of motion defines only the natural state of the motion of the body i. It does not allow us to quantify the force and acceleration of a body. The acceleration is the rate of change in velocity; it is caused only by an external force acting on it.
The second law of motion states that the net force on an object is equal to the rate of change of its linear momentum. Linear momentum of an object is a vector quantity that has both magnitude and direction. It is the product of mass and velocity of a particle at a given time:. From this equation, we see that objects with more mass will have more momentum. Picture two balls of different mass, traveling in the same direction at the same velocity.
If they both collide with a wall at the same time, the heavier ball will exert a larger force on the wall. It states: the net force on an object is equal to the rate of change of its linear momentum. From calculus we know that the rate of change is the same as a derivative.
When we the linear momentum of an object we get:. Force and Mass : This animation demonstrates the connection between force and mass. As we stated earlier, acceleration is the rate of change of velocity, or velocity divided by time. Sir Isaac Newton was a scientist from England who was interested in the motion of objects under various conditions.
In , he published a work called Philosophiae Naturalis Principla Mathematica , which contained his three laws of motion. These laws form the bases for mechanics. The laws describe the relationship between forces acting on a body, and the motion is an experience due to these forces. If object A exerts a force on object B, because of the law of symmetry, object B will exert a force on object A that is equal to the force acted on it:. A person in motion stays in motion with the same speed and in the same direction Seat belts are used to provide safety for passengers whose motion is governed by Newton's laws.
The seat belt provides the unbalanced force that brings you from a state of motion to a state of rest. Perhaps you could speculate what would occur when no seat belt is used.
There are many more applications of Newton's first law of motion. Several applications are listed below. Perhaps you could think about the law of inertia and provide explanations for each application. Acquire a metal coat hanger for which you have permission to destroy. Pull the coat hanger apart. Using duct tape, attach two tennis balls to opposite ends of the coat hanger as shown in the diagram at the right. Bend the hanger so that there is a flat part that balances on the head of a person.
The ends of the hanger with the tennis balls should hang low below the balancing point. Place the hanger on your head and balance it. Then quickly spin in a circle. What do the tennis balls do? Physics Tutorial. My Cart Subscription Selection.
You could supply the force by pushing the book. An unbalanced force is needed to change the speed or direction of the spacecraft.
Effects of Interia You can see the effects of inertia everywhere. As a more familiar example of inertia, think about riding in a car. You and the car have inertia. If the car comes to a sudden stop, your body tends to keep moving forward. When the car starts moving again, your body tends to stay at rest. You move forward because the car seat exerts an unbalanced force on your body. Materials Table cloth 2 unbreakable plates 2 unbreakable cups 2 forks, spoons, napkins The heavier the cups and plates, the better it works A textbook.
Procedure Start with the table cloth on a table or desk. Set the table as if for dinner.
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