Every action has an equal and opposite reaction. Note: All Khan Academy content is available for free at (www.khanacademy.org)

Note: All Khan Academy content is available for free at (www.khanacademy.org)

Newton's First Law (Galileo's Law of Inertia). Note: All Khan Academy content is available for free at (www.khanacademy.org)

We apply the Work-Energy theorem to a particle moving near the Earth's surface in order to derive the Conservation of Energy of the particle. We show that energy conservation holds regardless of the path that the particle follows provided that gravity is the only force that has a component in the direction of motion of the particle. If the particle moves on a rough track (friction force acting), we show that the final total energy (kinetic + potential) is less than the initial total energy. Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

We show that the work done by gravity on a mass m falling in a straight line (vertical or inclined) through height h is mgh. mgh is also the gravitational potential energy of the particle at height h above some reference level. We then state (without proof) that the work done by gravity on a particle moving down along any curved path is mgh where h is the vertical distance the particle moves through. Finally we apply the Work - Energy Theorem to connect the potential and kinetic energies of a falling particle. Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

The work done by the resultant force on a particle equals the change in the kinetic energy of the particle. We prove the theorem for the simplest case of a particle moving in a straight line, acted on by a constant resultant force pointing in the direction of motion of the particle. Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

The work done by the force on a particle is a scalar quantity and has units Nm or J (Joules). Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Newton's law of gravitation is explained and used along with Newton's Second law to show that g = 9.81m/s^2. We ignore air resistance and assume that the only (hence resultant) force on an object of mass m is the force due to earth's gravity. We also assume that the distance of the mass to the earth's surface is negligible compared to the radius of the earth. Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

The block is modeled as a particle, so Newton's Laws can be applied to it with good accuracy. The acceleration of any particle down a smooth incline is gSinϴ where ϴ is the angle of the incline. Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Sample problems involving pulley systems from exam papers. Check out KeysToMaths1 for more tutorials and solutions: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Sample problems involving friction. Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

The friction force opposes the motion of an object, so the friction force vector points in a direction opposite to the velocity vector of the object. Its magnitude varies from zero to a maximum called the limiting friction. Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

We look at the reading on a weighing scales for a particle of mass m that moves in an elevator with uniform acceleration a. This is the apparent weight of the particle. We show that apparent weight = mg + ma. Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Newton's third and second laws are used to explain the "obvious" fact that if a particle of mass m rests on a weighing scales, then the force on the scales is mg, the weight of the particle. The reading is often given in kg, so the force on the scales (in Newtons) is divided by g. Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Newton's Second and Third laws are used to determine the contact forces between a book and a horizontal surface. Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Newton's Third Law says that forces come in pairs, sometimes called Action - Reaction pairs. When an object A exerts a force on object B, object B "reacts" by exerting a force of equal magnitude but opposite direction on A. Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Tutorial on forces in one dimension. Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug

Check out KeysToMaths1 for more tutorials: https://www.youtube.com/channel/UCOYoe9L9R13HGUIhszjkeug