Gravitational Field A gravitational field as a region in which an object experiences a force due to gravitational attraction. Gravitational Field Strength The gravitational field strength at a point in the gravitational field is the gravitational force acting on a mass of 1 kg placed at that point. The unit of gravitational field strength is … Read more


Arrangement in series: Arrangement in parallel: Extension = x × number of springStiffness decreasesSpring constant = k/number of spring Extension = x ÷ number of springStiffness increasesSpring constant = k × number of spring Factors Affecting the Stiffness of Spring Stiffer Less stiff Material type of spring(A steel spring is stiffer than a copper spring) … Read more

Hooke’s Law

Hooke’s Law Hooke’s Law states that if a spring is not stretched beyond its elastic limit, the force that acts on it is directly proportional to the extension of the spring. Elastic Limit The elastic limit of spring is defined as the maximum force that can be applied to a spring such that the spring … Read more


Elasticity Elasticity is the ability of a substance to recover its original shape and size after distortion. Forces Between AtomsThe intermolecular forces consist of an attractive force and a repulsive force. At the equilibrium distance, d, the attractive force equal to the repulsive force. If the 2 atoms are brought closer, the repulsive force will … Read more


Efficiency The efficiency of a device is defined as the percentage of the energy input that is transformed into useful energy. Example:In the example above, the input power is 100J/s, the desire output power (useful energy) is only 75J/s, the remaining power is lost as undisire output. Therefore, the efficiency of this machine is Efficiency= … Read more


Power Power is the rate at which work is done, which means how fast a work is done. Formula: Example:An electric motor takes 20 s to lift a box of mass 20kg to a height of 1.5 m. Find the amount of work done by the machine and hence find the power of the electric … Read more

Potential Energy

Energy Energy is defined as the capacity to do work. Work is done when energy is converted from one form to another. The unit of work is Nm or Joule(J)   Gravitational Potential Energy Gravitational potential energy is the energy stored in an object as the result of its vertical position (i.e., height). Formula:   … Read more

Finding Work Done from a Graph

Finding Work from Force-Displacement GraphIn a Force-Displacement graph, work done is equal to the area in between the graph and the horizontal axis. Example:The graph above shows the force acting on a trolley of 5 kg mass over a distance of 10 m. Find the work done by the force to move the trolley.Answer:In a Force-Displacement graph, work done … Read more