Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Kinetic Energy

Sponsored Links

Work must be done to set any object in motion, and any moving object can do work. Energy is the ability to do work and kinetic energy is the energy of motion. There are several forms of kinetic energy

  • vibration - the energy due to vibration motion
  • rotational - the energy due to rotational motion
  • translational - the energy due to motion from one location to another

Energy has the same units as work and work is force times distance . One Joule is one Newton of force acting through one meter - Nm or Joule in SI-units. The Imperial units are foot-pound .

  • 1 ft lb = 1.356 N m (Joule)

Translational Kinetic Energy

Translational kinetic energy can be expressed as

E t = 1/2 m v2(1)


E t = kinetic translation energy (Joule, ft lb)

m = mass (kg, slugs )

v = velocity (m/s, ft/s)

  • one slug = 32.1740 pounds (as mass) - lbm

Rotational Kinetic Energy

Rotational kinetic energy can be expressed as

E r = 1/2 I ω2(2)


Em = kinetic rotation energy (Joule, ft lb)

I = moment of inertia - an object's resistance to changes in rotation direction (kg m2, slug ft2)

ω = angular velocity ( rad /s)

Example - Kinetic Energy in a Car

The kinetic energy of a car with mass of 1000 kg at speed 70 km/h can be calculated as

E t = 1/2 (1000 kg) ((70 km/h) (1000 m/km) / (3600 s/h))2

= 189043 Joule

The kinetic energy of the same car at speed 90 km/h can be expressed as

E t = 1/2 (1000 kg) ((90 km/h) (1000 m/km) / (3600 s/h))2

= 312500 Joule

Note! - when the speed of a car is increased with 28% (from 70 to 90 km/h ) - the kinetic energy of the car is increased with 65% (from 189043 to 312500 J ). This huge rise in kinetic energy must be absorbed by the safety construction of the car to provide the same protection in a crash - which is very hard to achieve. In a modern car it is possible to survive a crash at 70 km/h . A crash at 90 km/h is more likely fatal.

Download and print Kinetic Energy in a Moving Car chart


Example - Kinetic Energy in a Steel Cube moving on a Conveyor Belt

A steel cube with weight 500 lb is moved on a conveyor belt with a speed of 9 ft/s .  The steel cube mass can be calculated as

m = (500 lb ) / (32.1740 ft/s2)

= 15.54 slugs

The kinetic energy of the steel cube can be calculated as

E t = 1/2 (15.54 slugs) (9 ft/s)2

= 629 ft lbs

Example - Kinetic Energy in a Flywheel

A flywheel with Moment of Inertia I = 0.15 kg m2 is rotating with 1000 rpm (revolutions/min) . The angular velocity can be calculated as

ω = (1000 revolutions /min) (0.01667 min/s) (2 π rad/ revolution )

= 104 rad/s

The flywheel kinetic energy can be calculated

E r = 1/2 (0.15 kg m2) (104 rad/s) 2

= 821 J

Sponsored Links

Related Topics


Motion of bodies and the action of forces in producing or changing their motion - velocity and acceleration, forces and torque.


The relationships between forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more.

Related Documents

Angular Motion - Power and Torque

Angular velocity and acceleration vs. power and torque.

Car Acceleration

Car acceleration calculator.

Car Fuel Consumption - liter/100 km

Calculate fuel consumption in liter per km - consumption chart and calculator.

Conservation of Momentum

The momentum of a body is the product of its mass and velocity - recoil calculator.

Conveyors - Belt Speed

Maximum conveyor belt speed.

Distance Traveled vs. Speed and Time - Calculator and Chart

Velocity plotted in time used diagram.

Dynamic Pressure

Dynamic pressure is the kinetic energy per unit volume of a fluid in movement.

Energy Storage Density

Energy density - by weight and volume - for some ways to store energy

Flywheels - Kinetic Energy

The kinetic energy stored in flywheels - the moment of inertia.

Formulas of Motion - Linear and Circular

Linear and angular (rotation) acceleration, velocity, speed and distance.

Fuel Consumption - mpg

Calculate fuel consumption in miles per gallon - mpg - calculator and consumption charts.

Heat, Work and Energy

Heat vs. work vs. energy.

Impact Force

Impact forces acting on falling objects hitting the ground, cars crashing and similar cases.

Impulse and Impulse Force

Forces acting a very short time are called impulse forces.

Pitot Tubes

Pitot tubes can be used to measure fluid flow velocities by measuring the difference between static and dynamic pressure in the flow.

Potential Energy - Hydropower

Elevation and potential energy in hydropower.

Projectile Range

Calculate the range of a projectile - a motion in two dimensions.

Rolling Resistance

Rolling friction and rolling resistance.

Salt Hydrates - Melting points and Latent Melting Energy

Melting points and latent energy of salt hydrates.

Vehicle - Distance Traveled vs. Velcocity and Time Used (mph)

Speed (mph) and time (hours) and distance traveled (miles) chart.

Vehicle - Distance Traveled vs. Velocity and Time (km/h)

Speed (km/h) vs. time (hours) and distance traveled (km).

Wind Load vs. Wind Speed

Wind load on surface - Wind load calculator.

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.