Science Grade 9 – Quarter 4

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Written by rmha11

Curriculum Guide

  1. Motion in Two Dimensions
  • Projectile Motion
    • Impulse, Momentum and Impulse
    • Conservation of Linear Momentum

2. Work Power and Energy

  • Changes in form of mechanical energy
  • Conservation of energy

3. Heat, Work, and Efficiency

4. Electricity and magnetism

  • Power generation and energy losses
  • Transmission and distribution of electrical energy from power plants to homes

Lesson 2: Work, Power, And Energy

Objectives:

  • Trace and explain the energy transformations in various activities.
  • Perform activities to demonstrate conservation of mechanical energy.
  • Ascertain that the total mechanical energy remains the same during any process.

Mechanical Energy

The energy acquired by objects upon which work is done is known as mechanical energy.

Different Forms of Mechanical Energy:

A. Potential Energy – Energy in matter due to arrangements of its parts, its
composition, location and structure. It is commonly considered as a stored energy having the potential to do mechanical work.

PEgrav = mgh

PEgrav = gravitational potential energy
m = mass of object
g = acceleration due to gravity
h = height or elevation difference

PEelas = 1/2kx²

PEelas = elastic potential energy
k = spring constant
x = compression or extension length

B. Kinetic Energy – Energy in moving matter and wave.

KE = 1/2mv²

KE = kinetic energy
m = mass of object
v = velocity of object

Ignoring frictional force, the total mechanical energy, which is the sum of its kinetic and potential energies, remains constant at all points of the track.

ME1 = ME2 = ME3 = …
PE1 + KE1 = PE2 +KE2 = PE3 +KE3 = …

h = ½ agt² and vf = agt since vi = 0

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