How Do You Preserve Kinetic Energy?

Introducing Kinetic Energy

Kinetic energy is the energy of motion. An object that has motion – whether it is vertical or horizontal motion – has kinetic energy. Some examples of kinetic energy in everyday life include:

– A person walking or running

– A bicycle moving forward

– Balls bouncing

– Cars driving on the road

– An airplane flying through the sky

In physics, the kinetic energy (KE) of an object is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having increased velocity means an increase in kinetic energy.

Importance of Preserving Kinetic Energy

Preserving kinetic energy provides important benefits across many areas. Kinetic energy is the energy of motion, so being able to maintain the velocity and momentum of moving objects allows that energy to be reused or converted to perform useful work.

Some key applications where preserving kinetic energy is crucial include:

  • Vehicles – Minimizing braking loss allows kinetic energy to propel the vehicle farther.
  • Industry – Stopping high-speed machinery slowly recaptures energy rather than dissipating it as heat.
  • Renewables – Kinetic turbine systems generate electricity from passing winds or flowing water.
  • Sports – Athletes minimize exertion by preserving existing momentum in motions.
  • Batteries – Kinetic energy harvesters recharge batteries from ambient vibration.

Overall, preserving kinetic energy provides major benefits by reducing wasted energy, improving efficiency, generating power, and enabling motion. Developing technologies and systems to maintain velocity and momentum is key for applications where performance, sustainability, and productivity are priorities.

Factors that Reduce Kinetic Energy

There are three main factors that can reduce the kinetic energy of a moving object:


Friction occurs when two surfaces rub against each other. The friction converts some of the kinetic energy into thermal energy, causing the object to slow down. Sources of friction include air resistance, water resistance, rolling resistance with the ground, and mechanical friction in bearings and joints.

Air Resistance

Air resistance, or drag, acts in the opposite direction to an object’s motion. As an object moves through air, it has to push the air molecules out of the way. This air resistance removes kinetic energy from the object.

Inelastic Collisions

In an inelastic collision between two objects, some of the initial kinetic energy is converted to other forms like heat, sound and potential energy. The total kinetic energy of the two objects after the collision is less than before. Minimizing inelastic collisions helps preserve kinetic energy.

Minimizing Energy Loss from Friction

Friction results in loss of kinetic energy as heat, slowing down moving objects. There are several techniques to minimize energy loss from friction.

Using lubricants like oils and greases reduces friction between surfaces in contact. Lubricants work by forming a thin film that keeps the surfaces apart, reducing rubbing. Effective lubrication enables smoother motion and less waste of kinetic energy.

Smooth surfaces have less friction compared to rough surfaces. Polishing and smoothing surfaces minimizes friction as there are fewer high points that can rub against each other. A perfectly smooth surface can virtually eliminate friction when lubricated.

Low friction materials like teflon and specialized ceramics and alloys create less friction naturally. Replacing high friction materials like steel with low friction alternatives helps preserve kinetic energy.

Combining lubrication, surface smoothing, and low friction materials greatly reduces waste of kinetic energy through friction. This enables efficient transfer and usage of kinetic energy for work and motion.

Minimizing Air Resistance

One method for preserving the kinetic energy of a moving object is to minimize air resistance or drag. Air resistance will slow down a moving object as it pushes against the air. The kinetic energy of motion gets converted to heat and sound energy as the object moves through the air. By reducing air resistance with a streamlined design, less kinetic energy will be lost.

The most significant factor influencing air resistance is the shape or design of an object. Rounded and tapered shapes that minimize the frontal area exposed to airflow will have less drag. Examples include the curved front of high speed trains or the shape of airplanes’ wings. Other factors like surface smoothness and finishing can also minimize turbulence and friction from air passing over an object. The more streamlined an object is in its shape and features, the more readily it will be able to preserve its kinetic energy of motion by reducing drag from air resistance.

Designing for Elastic Collisions

One way to preserve kinetic energy during collisions is to design systems and objects to have elastic or partially elastic collisions. Elastic collisions are ones in which kinetic energy is conserved. This means the total kinetic energy of the system before and after the collision is the same.

On a macro scale, car designers utilize principles of elastic collisions. They design crumple zones on vehicles that compress and absorb some of the kinetic energy during a crash. The crumple zones act like springs, reducing impulse and preserving more kinetic energy.

Springs and shock absorbers are used in many machines and devices to create elastic collisions. The springs compress and expand, minimizing kinetic energy loss. This is why springs are used in everything from door hinges to vehicle suspension systems.

By understanding physics principles of elastic collisions, engineers can design systems that conserve kinetic energy even during collisions and impacts. This preserves the energy for continued use rather than losing it to destructive forces.

Recovering Kinetic Energy

Kinetic energy is often lost and wasted as heat or sound, but there are ways to recover some of that energy for later use. Two common methods are regenerative braking and flywheels.

Regenerative braking is a technique used in vehicles like electric cars and trains to recapture some of the kinetic energy that would normally be lost when braking. The vehicle’s electric motor switches roles and acts as a generator, converting the vehicle’s momentum into electricity that can be stored in batteries. This extends the vehicle’s range as it doesn’t have to waste energy slowing down.

Flywheels are mechanical devices that can store rotational kinetic energy. A heavy rotor spins at high speeds, maintaining angular momentum. When the energy needs to be recaptured, the flywheel’s rotation is gradually slowed down by a transmission system, generating electricity in the process. Flywheels are often used to smooth out power delivery in vehicles or provide backup power in case of interruptions.

Both regenerative braking and flywheels allow a portion of kinetic energy that would usually be lost as heat or noise to be recovered in a useful form for later use. This improves the efficiency of systems and takes advantage of energy that would otherwise be wasted.

Storing Kinetic Energy

There are several effective ways to store kinetic energy for later use:


A flywheel is a mechanical device that stores rotational kinetic energy. It consists of a heavy rotating wheel that maintains angular momentum by resisting changes in rotational speed. When an external force is applied to increase the flywheel’s spin, energy is added to the system. That energy can then be drawn back out at a later time to perform useful work.

Flywheels are often used in power tools, engines, and generators to smooth out the delivery of power between energy input and output. For example, a flywheel connected to a motor can continue spinning to deliver constant power when the motor slows down or stops between pulses.


Springs and other elastic devices can store kinetic energy when deformed through the compression or stretching of the elastic material. The kinetic energy makes the molecules move and deform away from their relaxed state. When released, the material springs back to its original shape, releasing the stored kinetic energy.

Springs are used in everything from toys and vehicles to industrial machines and clocks. They allow kinetic energy to be stored gradually by elastic deformation and released rapidly in a burst.

Gravitational Potential Energy

Lifting or raising an object against gravity increases its gravitational potential energy. This stored energy that can be converted back to kinetic energy when released. For example, pumped hydroelectric facilities convert cheap off-peak electric energy to gravitational potential energy by pumping water uphill to an elevated reservoir. When electricity demand is high, that reservoir water is released through hydro turbines, generating electricity from the kinetic energy.

gravitational potential energy can also be seen in objects at the top of an incline or rollercoaster before released to accelerate downwards from the conversion of potential energy to kinetic energy.

Converting Kinetic to Other Useful Forms

Kinetic energy can be converted into other useful forms of energy such as electrical energy. Here are two ways this can be accomplished:


Generators convert kinetic energy into electrical energy. They work by moving an electrical conductor like a wire through a magnetic field. This motion induces a voltage difference between the ends of the conductor. The voltage can then be used to power electrical devices.

Examples of generators converting kinetic energy include wind turbines, hydroelectric generators in dams, and stationary bicycle generators. In each case, the kinetic energy of wind, falling water, or pedaling is converted into useful electricity.

Piezoelectric Effect

Some materials exhibit the piezoelectric effect, meaning they generate an electric charge when mechanically stressed or deformed. The word “piezo” means pressure or squeezing.

Piezoelectric materials can directly convert kinetic energy from vibrations, collisions, or pressure into usable electrical energy. They are used in applications like igniters in barbecue grill lighters, buzzers in quartz watches, and ultrasound transducers.

By carefully choosing materials and design, kinetic energy can generate electricity through the piezoelectric effect. Researchers are exploring piezoelectric roads and sidewalks that could harvest energy from passing cars and pedestrians.

Real-World Applications of Preserving Kinetic Energy

Kinetic energy is frequently preserved in real-world systems and devices for practical applications. Here are some prime examples:

Hybrid and Electric Vehicles

Hybrid and electric cars use regenerative braking to recover kinetic energy that would normally be lost as heat when braking. This regenerative braking system converts some of the kinetic energy into electricity to charge the battery. By preserving kinetic energy this way, hybrids and EVs can extend their range and operate more efficiently.


Rollercoasters are designed to preserve kinetic energy using gravity and cleverly designed slopes, loops, hills and curves. By limiting unnecessary friction and air resistance, and using gravitational potential energy on the downhill parts to boost speed on the uphill sections, rollercoasters maximize thrills while minimizing the power needed to keep the ride going.

Industrial Energy Recovery

Many industries are implementing energy recovery systems to capture waste kinetic energy and reuse it productively. For example, regenerative braking systems in factory conveyor belts or heavy cranes can feed electricity back into the local grid. Energy recovery systems provide cost savings while also reducing net energy usage.

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