Examples

Examples of Kinetic Energy

We explain that what are some examples of kinetic energy? The kinetic energy is containing the bodies and substances for their movement. Everything that exists has a certain amount of kinetic energy because this is presented from subatomic particles and, at the same time, we are on a planet that is in constant motion, and it takes us with it through the universe.

Kinetic energy can be calculated at both the microscopic and macroscopic level . For example, for the calculations of this energy in the atoms or molecules of a gas there is the kinetic theory of gases, which already has established the equations that describe it. To obtain its value in visible objects with which we interact, the equation used is:

Ec = ½ mv 2

According to the equation, the kinetic energy is equal to the half product of: the mass of the body times the square of the speed at which it is moving . Using the units of the international measurement system: kilogram (kg) for mass, meters per second (m / s) for speed, we obtain with the equation the units kilogram-meter squared over second squared (kgm 2 / s 2 ), equal to Newton-meter (Nm), and this in turn to Joule (J). The Joule is the unit of energy .

Examples of kinetic energy

Below are calculated kinetic energy values ​​for different cases:

1.- What is the kinetic energy for an iron sphere that has a mass of 0.12 Kg and moves at a speed of 0.20 m / s?

Ec =?

m = 0.12 Kg

v = 0.20 m / s

Ec = ½ mv 2

Ec = ½ (0.12 Kg) * (0.20 m / s) 2

Ec = ½ (0.12 Kg) * (0.04 m 2 / s 2 )

Ec = ½ (0.0048 Kgm 2 / s 2 )

Ec = 0.0024 Kgm 2 / s 2

Ec = 0.0024 Joule

2.- What is the kinetic energy for a zinc bar that has a mass of 0.54 Kg and moves at a speed of 0.45 m / s?

Ec =?

m = 0.54 Kg

v = 0.45 m / s

Ec = ½ mv 2

Ec = ½ (0.54 Kg) * (0.45 m / s) 2

Ec = ½ (0.54 Kg) * (0.2025 m 2 / s 2 )

Ec = ½ (0.10935 Kgm 2 / s 2 )

Ec = 0.0547 Kgm 2 / s 2

Ec = 0.0547 Joule

3.- What is the kinetic energy for a sword that has a mass of 0.51 Kg and moves at a speed of 2.1 m / s?

Ec =?

m = 0.51 Kg

v = 2.1 m / s

Ec = ½ mv 2

Ec = ½ (0.51 Kg) * (2.1 m / s) 2

Ec = ½ (0.51 Kg) * (4.41 m 2 / s 2 )

Ec = ½ (2.2491 Kgm 2 / s 2 )

Ec = 1.1245 Kgm 2 / s 2

Ec = 1.1245 Joule

4.- What is the kinetic energy for a toy car that has a mass of 0.01 Kg and is moving at a speed of 1.2 m / s?

Ec =?

m = 0.01 Kg

v = 1.2 m / s

Ec = ½ mv 2

Ec = ½ (0.01 Kg) * (1.2 m / s) 2

Ec = ½ (0.01 Kg) * (1.44 m 2 / s 2 )

Ec = ½ (0.0144 Kgm 2 / s 2 )

Ec = 0.0072 Kgm 2 / s 2

Ec = 0.0072 Joule

5.- What is the kinetic energy for a vehicle that has a mass of 1350 Kg and is moving at a speed of 20 m / s?

Ec =?

m = 1350 Kg

v = 20 m / s

Ec = ½ mv 2

Ec = ½ (1350 Kg) * (20 m / s) 2

Ec = ½ (1350 Kg) * (400 m 2 / s 2 )

Ec = ½ (540000 Kgm 2 / s 2 )

Ec = 270000 Kgm 2 / s 2

Ec = 270000 Joule

6.- What is the kinetic energy for a rocket that has a mass of 4000 Kg and is moving at a speed of 40 m / s?

Ec =?

m = 4000 Kg

v = 40 m / s

Ec = ½ mv 2

Ec = ½ (4000 Kg) * (40 m / s) 2

Ec = ½ (4000 Kg) * (1600 m 2 / s 2 )

Ec = ½ (6400000 Kgm 2 / s 2 )

Ec = 3200000 Kgm 2 / s 2

Ec = 3200000 Joule

7.- What is the kinetic energy for a sedan car that has a mass of 1135 Kg and is moving at a speed of 32 m / s?

Ec =?

m = 1135 Kg

v = 32 m / s

Ec = ½ mv 2

Ec = ½ (1135 Kg) * (32 m / s) 2

Ec = ½ (1135 Kg) * (1024 m 2 / s 2 )

Ec = ½ (1162240 Kgm 2 / s 2 )

Ec = 581120 Kgm 2 / s 2

Ec = 581120 Joule

Kinetic energy and states of matter

Matter can appear in various physical states , but we can only interact in our reality with the three fundamentals: solid, liquid and gas . The others, such as plasma and two others treated in the laboratory, are not accessible for us to touch. The kinetic energy is the one that will define when a substance is solid, liquid or gaseous, by the following:

When the particles of matter have little motion , they carry little kinetic energy . They remain compact and forming an orderly structure that does not flow and remains with a defined shape. This is how the solid state is taken . Now, what will make the particles start to jiggle more is to give them more kinetic energy. This is achieved by increasing its temperature .  

The  temperature is the physical quantity that tells us the average kinetic energy of matter. There are four main scales on which it can be measured:

  • Celsius (° C) , from the international measurement system (SI). Based on the properties of water, it marks its melting point at 0 ° C and its boiling point at 100 ° C.
  • Kelvin (K) , from the international measurement system (SI). It is absolute, and marks the so-called absolute zero at 0 K (equal to -273.15 ° C), the melting point of water at 273.15K (0 ° C) and the boiling point of water at 373.15K (100 ° C) .
  • Fahrenheit (° F) , from the English system. Based on the properties of water, it marks its melting point at 32 ° F and its boiling point at 212 ° F.
  • Rankine (R) , from the English system. It is absolute, and marks the so-called absolute zero at 0 R (equal to -459.67 ° F), the melting point of water at 491.67 R (32 ° F), and the boiling point of water at 671.67 R (212 ° F) .

Having understood this, we know that when the temperature of a material rises , this is the same as its kinetic energy increases . When in a solid the particles move enough to begin to move over each other, it is said that a change of state occurs , towards the liquid state . The latter can take the form of the container that contains it.

When the kinetic energy in a liquid increases so much that its particles begin to escape from it and move into the air, the gaseous state has been reached . This will completely fill the closed container that contains it, making a uniform pressure towards all its walls. Similarly, if the gas is cooled, its kinetic energy will drop and the reverse transformation will begin.

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