Motion, Force, and Energy Motion consists of speed and direction When force is applied to an object, it changes its motion. Energy is an ability to change or move matter. Energy has the ability to change its form. Light can be refracted or reflected. Electricity flows in a circuit. Electricity can produce heat, light, sound, and magnetic effects. A vibrating object produces sound.

Force and Motion Motion is how an object moves or changes position. The length something travels is its distance. Speed is how fast an object moves. It is the distance an object travels in a specific amount of time. Apply what you learned on page 108.

Force Changes Motion All changes in movement are caused by force. Force is what pushes or pulls an object, causing it to change its speed or direction. Gravity is a force that pulls things towards the Earth. Friction helps to slow objects. If there were no friction an object would keep moving until another force stopped it.

Friction Friction is the force that occurs when two objects slide against each other. On Earth, moving objects encounter friction from the air and ground. In outer space, there is no friction or gravity. Objects will continue moving at the same speed or direction until they come into contact with some other force.

Friction Friction is greater between rough surfaces. In order to reduce friction in moving parts of machines, scientists and engineers use oil and other lubricants. Without friction, we would be unable to walk, sit in a chair, or climb up stairs. Too much friction will wear down moving parts.

Force, Mass and Gravity How much the speed of an object will change when force is applied depends on the amount of force and the size of the object. An object with greater mass requires more force to change its motion than an object with less mass. The force of gravity increases with the size of an object.

Energy Force is always created by some kind of energy. You cannot always see energy, but you sometimes feel it. Energy is an ability to cause changes in matter.

Kinds of Energy Heat Light/Solar Energy Electricity Sound

Heat Heat is caused by the movement of tiny particles in matter. As the particles move faster, the object heats up. Temperature tell show fast the particles are moving. Heat transfers from hotter objects to colder ones.

Light Light is another form of energy. Light comes from the energy given off by matter when tiny particles that make up matter collide with each other or are very hot. Light energy can move through water, air, and glass. Solar energy is a form of light energy. Dark colors absorb light. Light colors reflect light.

Reflection and Refraction Reflection involves the bouncing of a light ray off a surface. When light passes through a second substance at a different speed, the rays of light appear to bend. This bending of light is known as refraction.

Lenses A lens is a piece of glass or other material that is curved. A convex lens bends light rays towards each other. A concave lens bends light rays apart. Telescopes and eyeglasses use lenses to make objects appear clearer. Study the diagrams on page 115 for more detail.

Electricity Electricity is made by fast-moving charged particles. Electricity can flow easily through objects such as metal and water. These substances are known as conductors. Materials that do not conduct electricity, such as wood and rubber, are known as resistors.

Electric Circuits Electricity can flow in a circuit. A circuit must provide a continuous path for the particles to move through. A circuit is a system with several parts –A source that provides electricity –Something that uses electricity –Wires to carry the electricity back and forth

Other Properties of Electricity Magnetism—when electricity runs through a wire, the wire becomes magnetic. Heat—when electricity runs through some materials (resistors), it makes them hot. Light—when electricity runs through some materials, it makes them so hot they glow. Sound—Electricity is also capable of making sounds. Televisions, radios,and stereo speakers use electricity to make sounds. Electricity in nature causes thunder.

Sound Energy Sound is created by vibrating objects. The sounds of the vibrating object causes the air to vibrate. Our ears pick up these vibrations, and we hear those vibrations as sounds. Sound travels through many objects, including solids and liquids. Sound actually travels faster through many solids than air. The vibrations from a vibrating object spread out in waves.

Energy can Change its Form Electrical Energy can change to Light Energy –Electricity can run through a material that gets very hot and glows, such as a light bulb Solar Energy can change to Heat Energy –When you are outside on a sunny day, the suns energy heats your body Solar Energy can change to Chemical Energy –Through photosynthesis, plants change energy from the sun into chemical energy stored in food.