# Moving Objects

## Direction and Speed

When an object moves, or is in motion, it's position changes. The distance an object moves in a certain amount of time is called speed. For example, a car on the highway is moving at 60 miles per hour. This means that in one hour, which is the time interval, the car can travel 60 miles, the distance. The ratio of distance over time represents speed. A line graph is often used to show change in speed over time.

Objects in motion also have a direction. Whether it be up, down, North, South, East, West, or at a certain angle, direction can also vary. Speed in a certain direction is called velocity. Forces are what make objects change velocity

## Force

Force is the push or pull on an object that causes it to change speed and direction (velocity). Thus, a measurement of force must also have direction associated with it. Force is typically measured in Newtons (N).

The mass of an object also affects the amount of force it takes to change the velocity of the object. The greater the mass, the more force it takes to change speed and direction. For example, you push an empty box from rest to a speed of 3 meters per second. If that box was filled with books, it would take a much larger force to change the speed of the box from rest to 3 meters per second.

## Friction

Friction is one of the major forces of motion. It is the force between surfaces that slow down or stop an object from moving. For example, pushing a box across a marble floor most likely requires less force than pushing a box across a carpeted floor. This is because carpeted floors have more friction.

Additionally, if you give the box a shove across a surface, it will slow down and come to a stop in a certain distance. This is caused by frictional force from the contact of the box and the surface. In a world where friction does not exist, the box would keep sliding in the same direction at the same initial speed and never stop.

## Kinetic Energy

Kinetic energy is the energy of motion. Kinetic energy of an object is calculated by its velocity and mass. Kinetic energy can be transformed from potential energy, the energy stored in an object at an initial point.

Examples of objects that have kinetic energy include:

• Roller coasters

• A flying airplane

• Walking and running

• A thrown ball

## Electricity

Electricity is the flow of electric charge, or electrons and protons. The flow of these tiny, charged particles can produce energy. Most appliances in your home are powered by electricity. But how does the electricity flow through your house? Electricity usually flows through wires that conduct electricity. If we were to touch the wire will it was connected to electricity, we would shock ourselves. A protection, an insulator is placed around the metal conductor so we can safely operate with electric equipment.

### Conductors

Conductors are materials that are able to transfer electric current through them. Many metals are good conductors of electricity because their outer electrons are loosely attached.

Examples include:

• Iron

• Nickel

• Copper

### Insulators

Insulators are materials that are poor conductors or do not conduct electricity. Insulators do not transfer current because atoms are tightly grouped.

Examples include:

• Plastic

• Rubber

• Wood

## Circuits

A circuit is a loop that electricity can travel through. Circuits usually consist of wires to transfer electrons and an electrical source, like a battery. Electricity flows through the wires and can power devices. In a closed, or complete circuit, the wire connects back to the electrical source. Unless the circuit is complete, no electrons can move. A circuit in which there is no electron flow is called an open circuit. Switches can be placed in circuits to control whether the circuit is open or closed.

### Series Circuit

A series circuit is a circuit in which electric current follows one path. In a simple experiment, a wire is connected from a battery to (a) light bulb(s), and back to the other end of the battery. The connecting of the wire on both ends of the battery will cause the light bulb to light up. Electricity flows from the negative end of the battery to the positive end.

### Parallel Circuit

A parallel circuit is a circuit in which electric current follows in more than one path. Multiple wires are connected together and back to the battery. Parallel circuits have some advantages over series circuits. If you wire two light bulbs in a series circuit, they would both be dimmer than if there was only one. In a parallel circuit, the two light bulbs would still light up to their maximum brightness.