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Kinetic energy is all around us, from the motion of a bouncing ball to the speed of a rocket soaring through space. In this article, we'll break down the basics of kinetic energy, including how it's defined, how to calculate it, and the factors that affect it. Hence, if you are a curious student, then join us as we explore the fascinating world of kinetic energy and its role in powering the motion of our world.
What is Energy?
We can define energy as:
"The ability to do work is known as energy"
It is measured in joules (J) and is a scalar quantity, meaning it has magnitude but no direction.
There are different types of energy, including:
- Kinetic energy
- Gravitational potential energy
- Elastic potential energy
- Thermal energy
- Chemical energy
- Nuclear energy
It is important to understand the concept of energy and its different forms, as it is a fundamental concept that underlies many other topics, such as forces, work, power, and conservation of energy.
Definition of Kinetic Energy
The kinetic store of energy is defined as:
"The energy possessed by an object due to its mass and velocity"
Therefore, any object that is in motion possesses energy in its kinetic store. When an object accelerates (speeds up), energy is transferred to its kinetic store, and when it decelerates (slows down), energy is transferred away from its kinetic store.
Examples of Kinetic Energy From Everyday Life
Here are a few examples of kinetic energy from everyday life.
Rolling of a Ball
To understand kinetic energy, consider a ball rolling down a hill. As the ball rolls down the hill, it gains speed, and its kinetic energy increases. The kinetic energy of the ball is then converted into other forms of energy, such as sound and heat when it collides with an object or comes to a stop.
A Car Driving Down the Highway
As a car moves down the road, it possesses kinetic energy due to its mass and velocity. The faster the car goes, the more kinetic energy it possesses. This kinetic energy is converted into other forms of energy, such as heat and sound, when the car brakes or collides with another object.
A Basketball Being Thrown
When a basketball is thrown, it possesses kinetic energy due to its motion through the air. The faster and heavier the ball is thrown, the more kinetic energy it possesses. When the ball collides with the ground or a wall, its kinetic energy is converted into other forms of energy, such as sound and the deformation of the ball.
A Rollercoaster Moving Down a Track
As a rollercoaster moves down a track, it possesses kinetic energy due to its mass and velocity. The higher the rollercoaster is lifted, the more gravitational potential energy it has, which is converted into kinetic energy as the rollercoaster moves down the track.
A Running Person
When a person runs, they possess kinetic energy due to their motion. The faster the person runs, the more kinetic energy they possess. This kinetic energy is converted into other forms of energy, such as heat and sound when the person comes to a stop or collides with another object.
How to Calculate Kinetic Energy?
The formula for calculating kinetic energy is:
Kinetic energy =
Here, "m" stands for mass and "v" is for velocity. The mass is measured in kilograms (kg) and velocity is measured in meters per second (m/s). The units for kinetic energy are joules (J).
It is important to note that kinetic energy is a scalar quantity, meaning it has magnitude but no direction. This means that the direction of an object's motion does not affect its kinetic energy.
Example 1
If a vehicle has a mass of 2100 kg and it is moving at a speed of 16 meters per second, then what amount of kinetic energy is stored in it?
Follow the steps below to calculate the amount of kinetic energy stored in the vehicle:
Step 1: Find out the known quantities from the question
In the above question, there are two known quantities: mass and speed of the vehicle.
Mass of the vehicle, m = 2100 kg
Speed of the vehicle = v = 16 m/s
Step 2: Use the kinetic energy equation
The equation for kinetic energy is:
Step 3: Substitute values in the equation
After writing down the equation for kinetic energy, we just have to substitute the values to get the amount of energy stored in the vehicle.
Step 4 : Round the final value to 2 significant figures
In the last step, we can round the final answer to 2 significant figures.
Example 2
Calculate the kinetic energy of a baseball with a mass of 0.145 kg that is thrown at a velocity of 35 m/s.
Again, we will follow the same steps as in Example 1 to solve this problem.
Step 1: Find out the known quantities from the question
In the above question, there are two known quantities: mass and speed of the vehicle.
Mass of the basketball, m = 0.145 kg
Speed of the basketball = v = 35 m/s
Step 2: Use the kinetic energy equation
The equation for kinetic energy is:
Step 3: Substitute values in the equation
After writing down the equation for kinetic energy, we just have to substitute the values to get the amount of energy stored in the basketball.
Step 4 : Round the final value to 2 significant figures
In the last step, we can round the final answer to 2 significant figures.
Factors Affecting Kinetic Energy
Kinetic energy is determined by both the speed and mass of an object.
- Speed: If two objects move at the same speed, the one with a greater mass has a higher kinetic energy. This is because the kinetic energy is directly proportional to the mass of the object. For example, a truck and a car moving at the same speed have different kinetic energies because the truck has a greater mass.
- Mass: Just like speed, if two objects have the same mass, then the one that is moving at a higher speed has more kinetic energy. This is because the kinetic energy is proportional to the square of the velocity of the object. For example, a baseball and a tennis ball have the same mass, however, if the baseball is thrown at a faster speed than the tennis ball, it will have more kinetic energy.
Therefore, both mass and velocity are important factors that determine the kinetic energy of an object. An object with a larger mass and higher velocity will have more kinetic energy.
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