Forces
Introduction
Forces can be classified as a push or pull acting on an object. Everything from opening a drawer to the Earth's gravitational pull is known as a force. Can you think of other examples? Forces have the capacity to change either the state of motion or the state of mass in the object which it applies to.
You can also classify forces into two types: contact and non-contact force. However, it depends on if the forces are caused by contact or without it. They are known as contact and non-contact forces, respectively. To understand more clearly, you can refer to this example: A coin is falling from a building. Here, you will find two examples of forces. Can you find out what they are?
The first force is the gravitational force, which does not touch the coin, yet it still applies a force onto it in a downwards motion. The second is the frictional force: in this case, it does have contact with the coin: air resistance is formed due to friction, meaning the air molecules are rubbing against the coin's surface. Remember the examples of forces that you have thought of before? Now, try to find out whether they are examples of contact or non-contact forces.
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Classifications
The forces don't end there! Contact forces and non-contact forces have their sub-classifications. There are many examples, but we will talk about six main instances.
Contact Forces:
Applying forces on objects with your muscles can be considered muscular forces. Example: Opening a drawer, Pushing a trolley.
Applying forces on objects through the use of mechanics is called mechanical force. Example: The ticking of a watch, The turning of a fan.
The contact between two surfaces, one or both being in motion (Not at the same speed in the same direction), will generate an opposing force: friction. The quantity of the irregularities in both the surfaces will affect the amount of friction generated. Example: Book sliding on a table, Ants gripping the walls.
Non-contact Force
The attraction of one object to another because of its mass is known as gravitational force or gravity. Example: Skydivers jumping out of a plane, Two moons orbiting Mars.
The attraction or repulsion of two objects with at least one having magnetic properties and the other either being a magnet or one of some special metals is known as a magnetic force. For repulsion, you need both to be magnets. Like polarities will repel while opposite ones will attract. Example: Levitation in bullet trains, Magnetic stickers on the fridge.
The attraction or repulsion between electrically charged bodies is known as electrostatic force. Like magnetic force, like bodies repel while opposite bodies attract. Example: A balloon sticking on a wall, A lightning strike.
Counteraction
You can counteract forces. For example, take x as a particular amount of power. An object is traveling north with 6x velocity. Friction is counteracting with 1x power in the opposite direction. The result is a force of magnitude 5x in the northern direction. Can you find any other examples of counteraction of force? During a windy day, it is more difficult to cycle. In a tug of war competition, it is easier to pull the rope with more people pulling. To calculate the total force, called net force, you add the forces together. In our earlier example, the object is moving with 6x force. Friction is counteracting with 1x force in the opposite direction, that is, -1x force. 6x+(-1x) is equal to 5x. If there is an equal force in equal directions, the object may not move.
very handy, thanks Johan!
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