physics abc about energy 02

Physics ABC - About Energy 02

2021-06-03

What is Gravitational Potential?

The energy of an object due to being lifted or held above the ground is called Gravitational Potential Energy (GPE).

Gravitational Potential Energy means energy is stored to potentially make an object move.

We use Eg as the symbol of Gravitational Potential Energy.

If you climb higher, you get more GPE.

How to calculate Gravitational Potential?

Eg = mgh

(m is mass of object, g is gravity rate, h is height of object above referece level)

Because Eg = Fg * h * Cos0 = mg * h * 1 = mgh.

What is Kinetic Energy?

Kinetic Energy is the energy of an object due to its motion.

We use Ek as the symbol of Kinetic Energy.

How to calculate Kinetic Energy?

We know Ek = F * s * CosA.

Because F = ma (m is mass of object, a is the accelaration),

also, because a = (V2 - V1) / ∆t, and, s = Vavg * ∆t = ((V2 + V1) / 2) * ∆t

So:

Ek = F * s * CosA
= ma * s * CosA
= m * ((V2 - V1) / ∆t) * (((V2 + V1) / 2) * ∆t) * CosA
= m * ((V2² - V1²) / 2) * CosA

Ek = m * ((V2² - V1²) / 2) * CosA

Ek = (m * V²) / 2 (when V1=0 and CosA = Cos0 from the previous equation)

Mechanical Energy

The sum of an object’s kinetic energy and gravitational potential energy is called mechanical energy.

Emech = Ek + Eg