Energy and Its Forms 15.1 pg

Energy and Work Energy is the ability to do work – Energy is transferred by a force moving an object through a distance Work is a transfer of energy – When work is done on a n object, energy is transferred to that object

Example of work and energy: Carrying your backpack up stairs Lift it -- AGAINST the force of gravity REQUIRES energy from your MUSCLES Muscles REQUIRE energy from FOOD Food REQURIES energy from plants and other animals.

Extra info: Muscles use energy in order to contract Fischer and Krebs discovered how the breakdown of glycogen to glucose is controlled in the skeletal muscles, so that energy supply matches energy demand. 1. Acetylcholine is released from a motor nerve. This causes an entry of calcium into the muscle cell. 2. Calcium activates phosphorylase kinase - the first protein kinase discovered by Fischer and Krebs. 3. Phosphorylase kinase phosphorylates phosphorylase, which is activated 4. Glycogen is broken to glucose. This is used to generate ATP 5. The muscle works and requires energy in the form of ATP 6. The muscle contains muscle cells 7. Contractile proteins in the muscle are activated by calcium Copyright © Nobel Media AB 2011

Kinetic Energy (KE) Is the energy of motion Is the energy of motion – Depends on an objects velocity (speed) and mass The kinetic energy of any moving object depends upon its mass and speed The kinetic energy of any moving object depends upon its mass and speed Kinetic Energy (KE) = 1/2 m x v 2 Kinetic Energy (KE) = 1/2 m x v 2 – Where m = mass in kg and v = velocity in m/s

Sample Problem for KE: A 0.1 kg bird is flying at a constant speed of 8 m/s. What is the bird’s kinetic energy? – Given info: Mass = 0.1 kg Speed or v = 8 m/s – Step 1: KE = 1/2 mv 2 – Step 2: KE = 1/2 (0.1 kg) (8 m/s) 2 – Step 3: KE = 3.2 kgm 2 /sec 2 = 3.2 kgm/sec 2 m And because kgm/sec 2 is a Newton we can write… KE = 3.2 Nm And Nm is a Joule so finally…KE = 3.2 Joules

Potential Energy (PE) Energy that is stored because of position or shape – A stretched string on a guitar or a streched rubber band has potential energy (PE) Two types of PE: – Gravitational Potential Energy – Elastic Potential Energy

Gravitational Potential Energy(GPE) Potential energy that depends upon an object’s height An objects GPE depends on its mass, its height, and acceleration due to gravity Increases when an object is raised to a higher level GPE or PE = mgh – Where m is mass, g is gravity, and h is height

Sample Problem for PE A 50 kg diver is at the top of a 10 meter high diving platform. What is the diver’s potential energy? – Given info: Mass = 50 kg Height = 10 m Gravity = 9.8 m/sec 2 – Step 1: PE = mgh – Step 2: PE = 50 kg (9.8m/sec 2 )(10m) – Step 3: PE = 4900 kgm/sec 2 m And because kgm/sec 2 is a Newton we can write… PE = 4900 Nm And Nm is a Joule so finally…PE = 4900 Joules

Elastic Potential Energy (EPE) The potential energy of an object that is stretched or compressed Examples – Stretched Ukulele string, rubber band, etc. – Compressed Bouncing a ball, shocks on a car, etc.

Forms of Energy 1. Mechanical: – Both Kinetic and Potential together 2. Thermal 3. Chemical 4. Electrical 5. Electromagnetic 6. Nuclear

Mechanical Energy (ME) The energy associated with the motion and position of everyday objects Sum of an objects Potential and Kinetic Energy Does not include thermal, chemical or other forms of energy associated with the motion or arrangement of atoms or molecules ME = PE + KE

Thermal Energy Atoms in an object are always in motion The total PE and KE of the molecules make up its thermal energy Faster motion, more thermal energy

Chemical Energy Chemical Energy is the energy stored in chemical bonds. – When broken they release energy – All chemical compounds store energy Gives energy from food Warm from firewood Energy from coal

Electrical Energy Energy associated with electric charges – Batteries convert chemical energy into electric – Lightning bolts

Electromagnetic Energy Electromagnetic energy is a form that travels through space in the form of waves – Visible light – X rays – Gamma Rays – Microwaves

Nuclear Energy The energy that is stored in atomic nucleus – Nuclear power plants - fission - release energy – The sun - Fusion - release energy when nuclei combine

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