**Energy** is a property of objects which can be transferred to other objects or converted into different forms but cannot be created or destroyed. Common energy forms include the kinetic energy of a moving object, the radiant energy carried by light, the potential energy stored by an object’s position in a force field (gravitational, electric or magnetic), elastic energy stored by stretching solid objects, chemical energy released when a fuel burns, and the thermal energy due to an object’s temperature. All of the many forms of energy are convertible to other kinds of energy, and obey the law of conservation of energy which says that energy can be neither created nor be destroyed; however, it can change from one form to another.

In classical mechanics, linear **momentum** or translational **momentum**(pl. momenta; SI unit kg m/s, or equivalently, Ns) is the product of the mass and velocity of an object.

In mechanics and physics, **simple harmonic motion** is a type of periodic motion where the restoring force is directly proportional to the displacement and acts in the direction opposite to that of displacement.

Topical Notes, Problems, Presentations, Quiz, Test, Investigations and Videos |

Work |

Power |

Kinetic Energy |

Potential Energy: Gravitational and Elastic |

Conservation of energy |

Impulse |

Momentum |

Conservation of momentum |

Elastic and inelastic collisions |

Linear restoring forces and simple harmonic motion |

Simple harmonic motion graphs |

Simple pendulum |

Mass-spring systems |

Test your Understanding: Chapter 4 MCQ Quiz 1 Here Take Chapter 4 ReQuiz MCQ Quiz 2 Here |

Simple harmonic motion can serve as a mathematical model for a variety of motions, such as the oscillation of a spring. In addition, other phenomena can be approximated by simple harmonic motion, including the motion of a simple pendulum as well as molecular vibration. Simple harmonic motion is typified by the motion of a mass on a spring when it is subject to the linear elastic restoring force given by Hooke’s Law. The motion is sinusoidal in time and demonstrates a single resonant frequency. For a simple harmonic motion to be an accurate model for a pendulum, the net force on the object at the end of the pendulum must be proportional to the displacement. This will be a good approximation when the angle of swing is small.