Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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.