Physics Chapter on Energy and Motion

Study Notes

Kinetic energy is the energy possessed by a moving body.
Kinetic energy is dependent on the mass and speed of the body.
Kinetic energy is calculated with the following formula: KE = 1/2 * m * V^2.
- KE = Kinetic Energy (measured in Joules)
- m = mass (measured in kg)
- V = speed (measured in m/s)
To convert km/h to m/s, divide the value in km/h by 3.6.

Gravitational potential energy is the energy possessed by an object due to its position relative to a reference point.
This energy is dependent on the object's mass, the acceleration due to gravity, and the height or altitude of the object.
The gravitational potential energy is calculated using the following formula: GPE = m * g * z
- GPE = Gravitational Potential Energy (measured in Joules)
- m = mass (measured in kg)
- g = acceleration due to gravity (approximately 9.8 m/s^2)
- z = height/altitude (measured in meters)
The gravitational potential energy is dependent on the chosen reference level.
Below the reference level, the gravitational potential energy is negative.
On the reference level, the gravitational potential energy is zero.
Above the reference level, the gravitational potential energy is positive.
For objects with large dimensions, 'z' represents the height of the center of gravity.

Elastic potential energy is the energy stored in a deformed solid, such as a compressed or elongated spring, due to its elastic properties.
This stored energy can be used to do work when the object returns to its natural length.

Mechanical energy is the total energy of a moving object at a certain altitude, considering both potential and kinetic energy contributions.
Mechanical energy is the sum of potential and kinetic energy.
Mechanical energy is calculated as follows: ME = PE + KE.
- ME = Mechanical Energy (measured in Joules)
- PE = Potential Energy (measured in Joules)
- KE = Kinetic Energy (measured in Joules)

In the absence of friction and external forces such as motor traction, mechanical energy remains constant.
This is because any change in potential energy is compensated by an equal and opposite change in kinetic energy.
ME (initial) = ME (final)
The energy is transformed between potential and kinetic energy, but the total amount remains the same.

Friction causes a decrease in mechanical energy.
Mechanical energy is not conserved when there is friction.
The loss of mechanical energy is transformed into thermal energy, which we experience as heat.
This loss of mechanical energy is equal to the work done by friction.
The work done by friction can be calculated using the equation: Wf = - f * d
- Wf = Work done by friction
- f = frictional force
- d = distance traveled
When a force F is applied to overcome friction, the change in mechanical energy is equal to the work done by the force minus the work done by friction.
Em = (F – f) * d