Energy

What the heck is energy anyway? EnergyEnergy- the ability to do work If an object or organism does work (exerts a force over a distance to move an object) the object or organism uses energy. Work = force x distance ex. When stretching a sling shot, you do work, and energy is transferred to the sling shot Measured in the unit joules b/c work is a force x distance it is measured in Newtons x meters. These units are called joules. 1 N x m = 1 J= 1 kg x m 2 /s 2

Energy Living organisms need energy for growth and movement. You use energy when you hit a tennis ball, compress a spring, or lift a grocery bag. Energy is the ability to do work

Nature of Energy Energy is all around you! –Y–You can hear energy as sound. –Y–You can see energy as light. –A–And you can feel it as wind.

Living organisms need energy for growth and movement.

Types of Energy position, shape, or condition1. Potential energy- energy that an object has b/c of its position, shape, or condition of the object “energy of position” or “stored energy”Called “energy of position” or “stored energy” Stretched rubber band has potential energy b/c the 2 ends are far away from each other (elastic potential energy)

Gravitational potential energy Gravitational potential energy- any system of 2 or more objects separated by a distance; results from gravitational attraction b/w the objects ex. Apple in a tree Grav. PE = mass x free-fall acc. X height PE = mgh

Gravitational Potential Energy topmore grav. PEAn apple at the top of the tree has more grav. PE w/ respect to the Earth than a similar apple on a lower branch. two apples of different masses same heightheavier apple has more grav. PE than the lighter oneBut if two apples of different masses are at the same height, the heavier apple has more grav. PE than the lighter one

Types of Energy 2. Kinetic Energy- energy of a moving object due to the object’s motion -depends on mass & speed Kinetic energy = ½ x mass x speed squared KE = ½ x mv 2 in the KE equation, speed is squared so a small increase in speed produces a large increase in KE ex. Why car crashes are more dangerous at high speeds Atoms/molecules have KE b/c they are constantly in motion (KE ↑ as particles heat up or KE ↓ as particles cool down)

Mechanical vs. Nonmechanical potential energy A. Mechanical potential energy – energy that you can see on a large scale; you know that it is there b/c of the height ; Mechanical potential energy exists because of the relative positions of two or more objects. For example, a rock resting on the edge of a cliff in such a position that it will fall freely if pushed has mechanical potential energy. Water at the top of a dam has mechanical potential energy. A sled that is being held at the top of an icy hill has mechanical potential energy. B. Non-mechanical potential energy- energy that you CANNOT SEE that is present in chemical bonds ex. dynamite

Mechanical vs. Nonmechanical Kinetic energy A. Mechanical kinetic energy- Kinetic energy exists because of the relative velocities of two or more objects. Examples: If you push that rock, open the gate of the dam or let go of the sled, something will move. The rock will fall; the water will flow; the sled will slide down the hill. In each case the mechanical potential energy will be changed to mechanical kinetic energy. Another way of saying this is that the energy of position will be changed to the energy of motion. This is energy that is clearly visible; an object is moving. B Non-mechanical kinetic energy –energy that is NOT VISIBLE but you know that it is there b/c it is present in the atoms of a molecule (moving) ex. Solid, liquid, gas atoms moving (dance moves)

Kinetic Energy

Types of Energy 3. Mechanical energy- sum of the potential & kinetic energy in a system ex. Apples have potential energy when they are hanging above the ground, & they have kinetic & potential energy when they are falling ex. Roller coaster

Non-mechanical Energy does not affect motion on a large scalenon- mechanical energy.Energy that lies at the level of atoms & that does not affect motion on a large scale is sometimes called non- mechanical energy.

Can mechanical energy change to non-mechanical energy? Yes, as a result of air resistance and friction. Moving an object across another can result in heat through friction. This is conversion of the mechanical energy into thermal energy. In an electric motor, the (mechanical) rotation of the coils results in electrical current and therefore electrical energy.

Types of Energy 4. Chemical Energy- The amount of chemical energy associated w/ a substance depends in part on the relative positions of the atoms it contains formation of bonds and the breaking of bonds during chemical reactions ex. Burning a match B/c chemical energy depends on position, it is a kind of potential energy

Chemical Energy Energy that exists in the bonds that hold atoms together. When bonds are broken, chemical energy is released. Examples: Digesting food…bonds are broken to release energy for your body to store and use. Sports… your body uses energy stored in your muscles obtained from food. Fire–a chemical change.

Chemical Energy Fuel and food are forms of stored chemical energy (potential).

Types of Energy 5. Nuclear Energy- kind of potential energy stored by the forces holding subatomic particles together in the nuclei of atoms Nuclear Fusion- a type of reaction in which light atomic nuclei combine to form a heavier nucleus ex. How sun works Nuclear Fission- a single heavy nucleus is split into 2 or more lighter nuclei

Types of Energy 6. Electricity- results from the flow of charged particles through a wire or other conducting materials Lightning is caused by electrons traveling through the air b/w the ground & a thundercloud

Types of Energy 7. Electromagnetic Energy (Light)- travels from the sun to the Earth across empty space in the form of electromagnetic waves

Electromagnetic Energy Light is a form of electromagnetic energy. Each color of light (Roy G Biv) represents a different amount of electromagnetic energy. Electromagnetic Energy is also carried by X-rays, radio waves, and laser light.

Types of Energy 8. Thermal Energy is the kind of energy that is related to and/or caused by heat. When you boil a pot of water, you are contributing thermal energy or heat to the bottom of the pot. This thermal energy is then transferred to the water inside the pot. As the water molecules move faster (kinetic energy), they begin to get hotter. As they move faster and faster, each one tries to leap away from its neighbors and into the surrounding air to form water vapor, or steam. Once the water starts boiling, it turns into steam very quickly!molecule