Transcript Motion, Force, and Energy

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
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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.