Principle of Conservation of Energy

Another important physics principle that we learned in SPM is Principle of Conservation of Energy. In form 4 we've learned about these following energy;

i. Kinetic energy - energy due to movement ( 1/2mv^2)

ii. Gravitational potential energy - energy due to height or position of an object (mgh)

iii. Elastic potential energy - energy stored in an elastic material (1/2Fx)

iv. Heat energy (Q=mc@)

Meanwhile in form 5 u'll be learning the following energy:

i. Electrical energy (E=VIt)

ii. Nuclear energy

Ok..all these energy that u've learned will obey a physics principle called conservation of energy.

So what does this principle tells u??

Principle of conservation of energy states that;

1. energy can't be created or destroyed by human

2. energy can only be transformed from 1 form to another
3. total energy during the transformation is constant
Look at this video...

Statement 1 & 2 mean  we as human can only managed to transform those energy. For example a rotating fan transformed electrical energy into kinetic energy & some might escape  into heat.

Then applying statement 3, it means.. total initial energy= total final energy...

therefore...

 total electrical energy supplied = total of kinetic energy used + heat energy

In other words those energy trasformed in a rotating fan is conserved. If u noticed, the fan might cause some heat lost due to friction in its motor. So this heat is a wasted energy. By right a function of a fan is to rotate & let us feel cooler, not to make us sweat by releasing heat :)  .. If this is the case, we can say that the fan has some inefficiency in its job. 

Due to this reason we came across in a concept used to measure energy efficiency. 

Energy Efficiency = (output energy / input energy)  x 100

Efficiency's calculation is about getting the percentage. If we refer to case of the rotating fan again,  electrical energy supplied to the fan  is the input energy. Meanwhile the kinetic energy acts as its output energy. So by calculation,

Efficiency of the fan = [(Kinetic energy used) / (Electrical Energy) ] x 100

Let say from the calculation  its energy efficiency is about 80% . So mana pergi the balance 20 % ???? 

This is because 20 % of the energy has been wasted into heat. 

In real world its almost impossible to get a sytem or device that works 100% efficient. Even u as student  are not 100 % efficient :) ..Of course i will prove it to u...

• Let say in physic's exam, total given marks for paper 2 are 100 marks (i.e the input). 
• What u've answered correctly represents the output.
• Usually your output is less than 100 marks, or even worst whuch in some cases u dont even get more than 50 marks. 
• Thus your efficiency will be around 40 %. 

If thats the case, u should asked yourself mana hilang that 60% ?? .. u should keep asking what causes you to be so inefficient??? Identify those culprit that threatening u from becoming an efficient student....
Is it due to 'cinta monyet' things, or attitude problem?..or is it bcoz most of your time wasted due to your addiction towards internet unwanted activities such as too much social networking, gaming or pornography??? 

Once u've figure it out...i sincerely advice u to make a change b4 its too late   ..who knows with some attitude transformation u might be 90% efficient in November 2010. If u managed to do it..i'm pleased to say that an 'A+'  is within your grasp.

To summarize our today's discussion on conservation of energy, i highly recommend u to watch these videos..
Enjoy your revision ;)