Forces and motion .au

[Pages:5]Forces and motion are in everyday life. Force is another word for pushing and pulling. If you push or pull an object it sets the object in motion. Motion is another word for movement. Without forces and motion everything would not be able to move. A force must be applying against an object to set it in motion.

Forces

If you push or pull it is applying a force. Applying a force on an object changes its motion. There are two different types of forces. They are contact forces and act at a distance forces. Forces makes things move or change their motion. For example, pushing in a chair, is applying a force to the chair, it moves its position.

Different types of forces

Contact forces is a type of force. It is when two interacting objects are physically touching. Example, kicking a ball, you and the ball are interacting. Act at a distance forces is also a type of force. It is when two interacting objects aren't physically touching. Magnetism and gravity are both act at a distance forces.

Contact forces

There are many types of contact forces. The first is normal force. It is when two forces is acting upon an object. Example, if you put a book on a table, gravity is pulling it down but the table is pushing it up. Applied force is when a person moves an object across the room. A force is applied. Tension force is the force applied to a cable or wire that is anchored on opposite ends to opposing walls or other objects. The spring force is the force created by compressed or stretching spring. Depending upon how the spring is attached it can pull or push in order to create a force.

Friction

Friction is a contact force. It happens when two objects rub

against each other. It can be useful because it

allows you to walk without sliding. It can be

destructive to objects that rub then wear away.

The heavier the object the higher the friction.

Sliding Friction

There are four different types of friction. The first is static friction. It is friction that acts on unmoving objects. Static describes a stationary object. Once the force is greater than static friction it is no longer applied and will start moving. Sliding friction is the second type of friction. It occurs between two objects sliding past each other. Sliding friction

slows things down. It is produced when bumps on a surface stick together. Fluid friction is a force that needs fluid to help it move. The frictional force can be exerted either on the fluid or on the object through which the fluid moves. Water flowing through a hose and a kite flying through the air both experience fluid friction. Rolling friction acts over the area where the wheel is in contact with the surface. Rolling friction is much less than sliding friction. It depends on the material of the wheel and the type of surface the wheel is rolling across. Air resistance is a type of friction. It can speed things up or slow them down in the air.

Inertia

Inertia is not a force. It is the property of all things. The more mass it has the more inertia it has. It makes things harder or easier to move. Moving objects tend to stay moving. Stationary objects tend to stay stationary.

Non-contact forces

Earth's gravity makes Moon orbit around it.

The main non-contact force is gravity. Gravity is a force that pulls objects down. The size of the pull depends on the objects mass. The gravitational force between Earth and the molecules of gas in the atmosphere is strong enough to hold the atmosphere close to our surface. The suns gravitational

pull keep our planet orbiting the sun. the motion of the moon is affected by the Suns gravity and the Earths.

Magnetism is the second main non-contact force. Magnetism is the force where objects attract or repel each other. Magnetic fields are invisible to the human eye. Magnets only attract certain types of metal. Iron, nickel and cobalt are attracted. Copper, silver, gold, magnesium, platinum and aluminium aren't attracted.

Motion

Without motion everything can't move. Every object has motion. Acceleration is a measure of how much velocity an object changes in a certain time. Velocities increase or decrease over time.

Important people

Isaac Newton

Albert Einstein

Albert Einstein and Isaac Newton are the greatest scientists

of all time. Albert Einstein explained how gravity works. He

also discovered details about gravity that Newton didn't

discover. Sir Isaac Newton was believed to be the greatest

English mathematician. He was the first to discover gravity.

He also discovered that the force that pulls things down is

the same as the force that makes the Moon orbit around Earth.

If you push or pull an object it changes its motion. A force must be applying against an object to set it in motion. Forces and motion are always going to be part of life.

By Charlie

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