energy and its forms 15.1 pg 446-452. energy and work energy is the ability to do work – energy is...

Energy and Its Forms

15.1 pg 446-452

Energy and WorkEnergy 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

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Example of work and energy: Carrying your backpack up stairsLift it -- AGAINST the force of gravityREQUIRES energy from your MUSCLESMuscles REQUIRE energy from FOODFood REQURIES energy from plants and

other animals.

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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 activated4. Glycogen is broken to glucose. This is used to generate ATP5. The muscle works and requires energy in the form of ATP6. The muscle contains muscle cells7. Contractile proteins in the muscle are activated by calciumCopyright © Nobel Media AB 2011





Kinetic Energy (KE)

Is the energy of motionIs the energy of motion– Depends on an objects velocity Depends on an objects velocity

(speed) and mass(speed) and massThe kinetic energy of any moving The kinetic energy of any moving

object depends upon its mass and object depends upon its mass and speedspeed

Kinetic Energy (KE) = 1/2 m x vKinetic Energy (KE) = 1/2 m x v22

– Where m = mass in kg and v = Where m = mass in kg and v = velocity in m/svelocity 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 kgSpeed or v = 8 m/s

– Step 1:KE = 1/2 mv2

– Step 2:KE = 1/2 (0.1 kg) (8 m/s)2

– Step 3:KE = 3.2 kgm2/sec2

= 3.2 kgm/sec2 m And because kgm/sec2 is a Newton we can write… KE = 3.2 NmAnd 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 kgHeight = 10 mGravity = 9.8 m/sec2

– Step 1:PE = mgh

– Step 2:PE = 50 kg (9.8m/sec2)(10m)

– Step 3:PE = 4900 kgm/sec2 m

And because kgm/sec2 is a Newton we can write… PE = 4900 NmAnd 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

together2. Thermal 3. Chemical4. Electrical5. Electromagnetic6. 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

energyGives energy from foodWarm from firewoodEnergy 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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