If I push on something or pull on it, then I am applying a force to it. Force makes things move or, more accurately, makes things change their motion. Two natural forces that we have experienced are the force of gravity and magnetic forces magnetic forces. These two forces act at a distance and do not require direct contact between the objects to function.
Gravity produces a force that pulls objects towards each other, like a person towards the ground. It is the force that keeps the Earth revolving around the sun and it's what pulls you toward the ground when you trip. See Science Trek's site on Gravity. Magnetism produces a force that can either pull opposite ends of two magnets together or push the matching ends apart.
A magnet also attracts objects made of metal. There are 6 kinds of forces which act on objects when they come into contact with one another. Remember, a force is either a push or pull. The 6 are:. A book resting on a table has the force of gravity pulling it toward the Earth. But the book is not moving or accelerating, so there must be opposing forces acting on the book.
This force is caused by the table and is known as the normal force. If you place a thin piece of wood or plastic a ruler works so that it is supported by both ends by books perhaps and place a small heavy object in the center, the piece of wood will bend.
Of course it wants to straighten out so it exerts an upward force on the object. This upward force is the normal force. You can feel the force yourself if you push down in the center of the piece of wood. The harder you push, the more the wood bends and the harder it pushes back. Applied force refers to a force that is applied to an object such as when a person moves a piece of furniture across the room or pushes a button on the remote control.
A force is applied. Frictional force is the force caused by two surfaces that come into contact with each other. Friction can be helpful as in the friction that allows a person to walk across the ground without sliding or it can be destructive such as the friction of moving parts in a motor that rub together over long periods of time.
Tension force is the force applied to a cable or wire that is anchored on opposite ends to opposing walls or other objects. This causes a force that pulls equally in both directions. The spring force is the force created by a compressed or stretched spring.
Depending upon how the spring is attached, it can pull or push in order to create a force. Resisting force , like air resistance or friction, change motion. Whether the forces actually stop or slow something depends upon your point of view. Air friction makes a leaf travel along in the wind. When you pick up a pencil, it's friction with your fingers that gets the pencil in motion. In each case, the friction makes the two things like the air and the leaf move together. Inertia is actually not a force at all, but rather a property that all things have due to the fact that they have mass.
The more mass something has the more inertia it has. You can think of inertia as a property that makes it hard to push something around. Friction is a force that happens when objects rub against one another. Say you were pushing a toy train across the floor.
It doesn't take much effort or force, because the toy is light. Now say you try to push a real train. You probably can't do it because the force of friction between the train and the ground is more intense. Examples of action-at-a-distance forces include gravitational forces. For example, the sun and planets exert a gravitational pull on each other despite their large spatial separation. Even when your feet leave the earth and you are no longer in physical contact with the earth, there is a gravitational pull between you and the Earth.
Electric forces are action-at-a-distance forces. For example, the protons in the nucleus of an atom and the electrons outside the nucleus experience an electrical pull towards each other despite their small spatial separation.
And magnetic forces are action-at-a-distance forces. For example, two magnets can exert a magnetic pull on each other even when separated by a distance of a few centimeters. Force is a quantity that is measured using the standard metric unit known as the Newton. A Newton is abbreviated by an "N. Thus, the following unit equivalency can be stated:. A force is a vector quantity. As learned in an earlier unit , a vector quantity is a quantity that has both magnitude and direction.
To fully describe the force acting upon an object, you must describe both the magnitude size or numerical value and the direction. Thus, 10 Newton is not a full description of the force acting upon an object. In contrast, 10 Newton, downward is a complete description of the force acting upon an object; both the magnitude 10 Newton and the direction downward are given.
Because a force is a vector that has a direction, it is common to represent forces using diagrams in which a force is represented by an arrow. Such vector diagrams were introduced in an earlier unit and are used throughout the study of physics.
The size of the arrow is reflective of the magnitude of the force and the direction of the arrow reveals the direction that the force is acting. Such diagrams are known as free-body diagrams and are discussed later in this lesson. Furthermore, because forces are vectors, the effect of an individual force upon an object is often canceled by the effect of another force. For example, the effect of a Newton upward force acting upon a book is canceled by the effect of a Newton downward force acting upon the book.
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