 ## Structure Questions – Understanding Energy

Diagram 5.1 (a) shows a boy skating down a ramp from position (X). Diagram 5.1 ((b)) shows the velocity-time graph of the boy from (X) to (Z). Diagram (5.2(a)) shows the same boy skating down from position (Y) by using another ramp. Diagram (5.2(b)) shows the velocity-time graph of the boy from (Y) to (Z). … Read more

## Kinetic Energy

Kinetic EnergyKinetic energy is the energy of motion. Equation of Kinetic Energy ExampleDetermine the kinetic energy of a 2000-kg bus that is moving with a speed of 35.0 m/s. Answer: Kinetic Energy,

## Gravity

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

## Spring

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 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

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 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

## Relationship between Energy and Work Done

During a conversing of energy, Amount of Work Done = Amount of Energy Converted Example:A trolley of 5 kg mass moving against friction of 5 N. Its velocity at A is 4ms-1 and it stops at B after t seconds. What is the work done to overcome friction?Answer:In this case, kinetic energy is converted into … 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