What is energy
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WHAT IS ENERGY? PowerPoint PPT Presentation


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WHAT IS ENERGY?. ENERGY. ENERGY: ability to do work. Whenever work is done, energy is transformed or transferred to another system. SI Units: joules (J). POTENTIAL ENERGY. energy that an object has because of position, shape, or condition stored energy. ELASTIC POTENTIAL ENERGY.

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WHAT IS ENERGY?

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What is energy

WHAT IS ENERGY?


Energy

ENERGY

ENERGY:

  • ability to do work.

    Whenever work is done, energy is transformed or transferred to another system.

    SI Units:

  • joules (J)


Potential energy

POTENTIAL ENERGY

  • energy that an object has because of position, shape, or condition

  • stored energy.


Elastic potential energy

ELASTIC POTENTIAL ENERGY

  • energy stored in any type of stretched or compressed elastic material.

  • spring

  • rubber band


Gravitational potential energy

GRAVITATIONAL POTENTIAL ENERGY

  • energy stored in gravitational field which exists between any two or more objects.

  • depends on both mass and height.

  • PE = mgh


  • Gravitational potential energy1

    GRAVITATIONAL POTENTIAL ENERGY

    A 65 kg rock climber ascends a cliff. What is the climber’s gravitational potential energy at a point 35 m above the base of the cliff?

    GIVEN:

    m = 65 kg

    h = 35 m

    g= 9.8 m/s2

    PE = ?

    WORK:

    PE = mgh

    PE = (65 kg) (35 m) (9.8 m/s2)

    PE = 2.2 x 104kg•m2/s2

    2.2 x 104 J


    Kinetic energy

    Kinetic Energy

    • energy of a moving object due to object’s motion

    • depends on mass and speed.

    • depends on speed more than mass.


    Kinetic energy1

    KINETIC ENERGY

    What is the kinetic energy of a 44 kg cheetah running at 31 m/s?

    GIVEN:

    KE = ?

    m = 44 kg

    v= 31 m/s

    WORK:

    KE = ½ mv2

    KE = ½ (44 kg) (31 m/s)2

    KE = 2.1 x 104 kg x m2/s2 or 2.1 x104 J


    Kinetic energy2

    KINETIC ENERGY

    Calculate the kinetic energy in joules of a 1500 kg car moving at 29 m/s.

    GIVEN:

    KE = ?

    m = 1500 kg

    v= 29 m/s

    WORK:

    KE = ½ mv2

    KE = ½ (1500 kg) (29 m/s)2

    KE = 6.3 x105 J


    Kinetic energy3

    KINETIC ENERGY

    Calculate the kinetic energy in joules of a 1500 kg car moving at 18 m/s.

    GIVEN:

    KE = ?

    m = 1500 kg

    v= 18 m/s

    WORK:

    KE = ½ mv2

    KE = ½ (1500 kg) (18 m/s)2

    KE = 2.4 x105 J


    Other forms of energy

    OTHER FORMS OF ENERGY

    MECHANICAL ENERGY:

    • amount of work an object can do because of object’s kinetic & potential energies

    • you can SEE it

    • Large scale basis

      NONMECHANICAL ENERGY.

    • you CANNOT SEE it

    • X rays, microwaves

    • Small scale basis (atomic)


    Other forms of energy1

    OTHER FORMS OF ENERGY

    ATOMS AND MOLECULES

    • kinetic energy of particles related to heat and temperature.

      CHEMICAL REACTIONS

    • Breaking bonds exothermic/endothermic

      PHOTOSYNTHESIS

    • turn energy in sunlight into chemical energy.


    Other forms of energy2

    OTHER FORMS OF ENERGY

    NUCLEAR FUSION /FISSION REACTIONS

    • Combining or splitting of atomic nuclei

      ELECTRICITY.

    • flow of charged particles

    • bolt of lightning or in a wire.

      ELECTROMAGNETIC WAVES.

    • Light energy (solar) from sun

    • X rays


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