You may have tuned out during explanations about mechanical energy in high school physics class. But you may also be surprised at how much this fascinating form of energy exists all around us.You may have tuned out during explanations about mechanical energy in high school physics class. But you may also be surprised at how much of this fascinating form of energy exists all around us.
When LeBron James shoots a hoop, the basketball has mechanical energy in midair. When a wrecking ball demolishes a house, that’s mechanical energy.
Mechanical energy is one of the world’s driving forces. Let’s dive into the illuminating world of energy to understand how this power shapes our lives.
What Is Mechanical Energy?
First, we need to understand energy. When we talk about energy, we talk about the ability to do work. We’ve learned how to manipulate energy so that it changes form from one type of energy to another. This change allows us to use energy to walk or cook or light our homes.
Energy comes in many types, including light, heat, sound, motion, gravitational, chemical, nuclear, and electrical.
Mechanical energy is one of these energy forms. Mechanical energy is the ability of an object to do work. That object’s energy is stored in the tension within it. The amount of work that an object can do depends on two basics: its motion and its position.
You may remember hearing about potential energy and kinetic energy in school. Potential energy is the energy of position, and kinetic energy is the energy of motion.
Think about something falling, like a pear from a tree. That pear’s kinetic energy is mechanical energy. A compressed spring is an example of stored mechanical energy, its energy coming from its compressed position or its potential energy.
Therefore, we can see that there are types of mechanical energy. One comes from potential energy and position, and the other from kinetic energy and motion.
What Is Mechanical Energy for Kids?
Mechanical energy is the energy that makes an object move. When a child pedals a bike, they use mechanical energy to pedal it. The faster they pedal, the more mechanical energy there is. A youngster dropping a ball from their window to bounce outside is also watching mechanical energy. The higher the window, or the heavier the ball, the more mechanical energy there is.
What Are 5 Mechanical Energy Examples?
The energy of motion can be seen in our everyday lives. Here are some examples of mechanical energy explained. Remember that mechanical energy is the ability of an object to do work.
- Wind turbines: Wind energy can be converted into electrical energy via wind turbines. Wind contains kinetic energy as it moves. This movement rotates the turbines’ blades and also the electricity-producing turbine within. Energy conversion has occurred; the wind’s kinetic energy has become electrical energy. That was completed thanks to mechanical energy, which gave the wind the capability of doing work.
- Wrecking balls: Buildings demolished by wrecking balls show mechanical energy in action. The wrecking ball has potential energy at the top of its swing. Once released, the wrecking ball follows a circular motion, traveling with kinetic energy. The moment the ball hits the building is when the wrecking ball’s ability to do work reveals itself. Force applies to the building and destroys it.
- People: Humans are excellent examples of mechanical energy. When we eat food, our stomachs break down food’s chemical potential energy to give us chemical energy to power our bodies. This energy means we can hop on a bike and apply force to the pedals, moving the bike. The pedaling motion is a type of mechanical energy.
- Nuclear power plants: Heat, or thermal energy, created by nuclear fission, turns turbines to produce electricity at nuclear power plants. The turning of generators in the nuclear energy industry is an example of mechanical energy.
- Roller coasters: As well as being fun to ride, roller coasters are a fantastic example of mechanical energy. There are no engines in roller coasters. They are winched up to a high point to give the heavy roller coaster a lot of potential energy. Then, the roller coaster has the ability to do work, using kinetic energy to move around the rails. It slows partly because of the frictional force of the wagon wheels and the rails. More on that later.
We can see how these objects gain kinetic energy while losing potential energy. Mechanical energy uses kinetic and potential energy and switches backward and forward between both.
Let’s get a better understanding of potential and kinetic energy before we look further into mechanical energy.
What Is Potential Energy?
Potential energy, or stored energy, is the energy of position. An object can have different amounts of potential energy because of its position. That’s to say that the potential energy of an object changes depending on where it is.
Think about a can of fruit on the floor. It doesn’t have much potential energy. It can’t move very far by itself, and there are no nearby moving objects to shift it. Ants can wander harmlessly around it.
Lift that can of fruit onto a shelf, and balance it at the shelf’s edge. Our humble can of fruit now has a lot more potential energy thanks to our object’s position. It could hurt your foot or the cat or even kill those pesky ants if it falls.
Moving the can of fruit to the shelf has bestowed it gravitational potential energy. The Earth’s gravitational forces provide the can potential energy, storing it thanks to its new vertical position. We know the Earth’s gravitational pull is strong. The denser the object, the more gravitational potential energy it possesses.
Suppose we increase the mass of the object on the shelf by swapping the can of fruit for a 10-pound doorstop. Despite being in the same position, the doorstop has more gravitational potential energy than the fruit. The doorstop can do more work and has more energy. The doorstop may break your foot if it fell, rather than causing a bruise like the can of fruit.
Potential energy can also be stored in an object through stretching or compression. This is called elastic potential energy, as is found in our compressed spring from earlier. A compressed spring releases its energy once uncompressed. Similarly, when you stretch that spring, it releases its potential energy to return to its normal state. Springs are used in car shock absorbers, their mechanical energy absorbing the bumps in the road.
Another way to imagine elastic potential energy is an archer stretching an arrow on a bow. The elastic string gains elastic potential energy. Upon release, that elastic potential energy shoots the arrow toward its new destination.
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What Is Kinetic Energy?
We’ve seen how to “build up” potential or stored energy in objects. We know kinetic energy is the energy of motion and movement.
We’ve also imagined how the potential energy of our can of fruit, once falling from the shelf, converts its potential energy into kinetic energy as it plummets to the ground. That fall shows how the can’s energy changes from potential energy (stored) energy to kinetic energy (motion).
The faster an object moves, the more kinetic energy it has. The more mass the object has, the more kinetic energy it has, too.
Let’s think about LeBron James shooting hoops. He takes aim and fires his shot. The basketball heads up and starts to lose speed due to gravity. The ball’s kinetic energy decreases. He scores! The ball increases speed as it leaves the hoop and heads to the ground.
The game is over, and LeBron accepts a challenge to throw a basketball as high and as far as he can. These throws will have much more kinetic energy in the basketball because it moves faster.
We unveil his opponent: a super-strong robot. The robot throws a bowling ball twice as heavy at the same speed as LeBron threw the one-and-a-half-pound basketball. Our robot’s bowling ball has more kinetic energy because it is heavier. Next, the robot throws its heavier ball twice as fast; again, we’ve added to the ball’s amount of kinetic energy by making it move more quickly.
Mechanical Energy, Potential Energy, and Kinetic Energy Together
Let’s recap the types of energy we’ve looked at:
- Mechanical energy: the ability of an object to do work
- Potential energy: stored energy in an object, its potential to do work, be that gravitational or elastic potential energy
- Kinetic energy: the energy of movement
These three energies all interact. It’s vital to understand that the law of conservation of energy dictates that energy cannot be destroyed or created, only converted from one energy type to another.
The law of conservation allows us to work out the mechanical energy of an object and the net force and total mechanical energy within a system.
How Do You Calculate Mechanical Energy?
Mechanical energy is measured in joules.
To work out the mechanical energy of the system we are studying, we need to know its potential energy and kinetic energy values, then add them together.
The formula for potential energy is PE = mgh.
- PE: the object’s potential energy
- m: the object’s mass in kilograms
- g: the Earth’s gravitational acceleration, defined as 9.8 m/sec2
- h: the object’s height above the Earth’s surface in meters
So, a ten-kilogram dumbbell (22 pounds) held two meters (six feet and five inches) from the ground would have the following potential energy: PE = 10 (kg) x 9.8 x 2 = 196 joules.
We calculate kinetic energy with this formula: KE = ½ m v2.
- KE: the object’s kinetic energy
- m: the object’s mass in kilograms
- v: the object’s speed in meters per second
Let’s drop our dumbbell from head height and assume it falls at two meters per second (6’ 5” per second). That gives: KE = 0.5 (½) x 10 (kg) x 2 (velocity) squared = 20 joules.
The formula for mechanical energy is PE + KE. In this example, our dumbbell has 196 (PE) + 20 (KE) = 216 joules of mechanical energy.
What Is the Definition of the Conservation of Mechanical Energy?
So far, we’ve examined systems and examples where the energy remains the same within the system. We’ve assumed that systems, like the roller coaster, see energy switch from potential to kinetic energy with no energy lost.
This is called the theorem of the Principle of Conservation of Mechanical Energy, which assumes the total mechanical energy of an object doesn’t change.
However, energy may be lost within these systems because of external and frictional forces. These frictional forces are called non-conservative forces. They take energy from a system. With our roller coaster, these non-conservative forces could be air resistance as the carriages whizz around. Energy can also be lost as thermal energy as the wheels heat the tracks.
Any energy lost as a non-conservative force acts upon a system cannot be recuperated. There is another way mechanical energy is lost — collisions.
How Much Mechanical Energy Is Lost in a Collision?
Think back to our wrecking ball. When it collides with a building, a wrecking ball dislodges masonry, makes a terrific sound, and moves walls. This impressive event is a type of collision and energy loss.
There are two types of collisions: elastic and inelastic.
An elastic collision results in no energy leaving a system. This idea would mean two objects banging into each other and setting off in a new direction with no speed loss at all. A perfectly elastic collision is probably unachievable. A Newton’s Cradle is perhaps the closest example of a perfect elastic collision, with very little energy lost each time the balls smack into each other.
An inelastic collision sees kinetic energy lost during a collision and is the most common collision type. A ball won’t bounce as high as the height from which it was dropped. Two cars crashing don’t carry on afterward at the same speed, just like bumper cars at a carnival.
Where Can You Find Mechanical Energy?
In reality, mechanical energy is all around us. Moving objects have mechanical energy. Stationary objects can have mechanical energy, too — potential energy. For example, a mountain choked with snow may appear still until its stored mechanical energy comes racing down as an avalanche.
Is Mechanical Energy Renewable?
Mechanical energy is not itself renewable. But there is renewable mechanical energy.
Renewable energy, by definition, is an energy that replenishes itself. That could be the sun powering solar panels or wind energy. Mechanical energy is the ability of an object to do work, which is different.
An example of renewable mechanical energy is hydroelectric power. Water’s renewable energy spins turbines at hydro plants to create electricity. There is mechanical energy at work with the water spinning the turbines, the ability to do work.
Mechanical energy itself is not renewable. But we can call this renewable mechanical energy because the hydropower element is renewable — and keeps renewing — and continues to create mechanical energy.
Mechanical Energy Is Everywhere
Mechanical energy, the ability of an object to do work, is everywhere. It can be stored in an object as potential energy or seen while an object moves as kinetic energy. It can also switch between those two energy types.
Objects that can do work are useful in our day-to-day lives. We’ve harnessed mechanical energy to create cars, kettles, power stations, and more. Modern living wouldn’t be the same without our understanding of mechanical energy.
Our knowledge of mechanical energy will be vital as we battle climate change. Renewable energy sources that create electricity are pivotal to tempering global warming. Mechanical energy is an intrinsic part of that clean energy process.
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