Jet Propulsion - Calculate the propulsive discharge force or thrust induced by an incompressible jet flow.Impulse and Impulse Force - Forces acting a very short time are called impulse forces.Fuel Consumption - mpg - Calculate fuel consumption in miles per gallon - mpg - calculator and consumption charts.Force - Newton's third law - force vs.Driving Distance between European Cities - Driving distance between some major European cities.Conservation of Momentum - The momentum of a body is the product of its mass and velocity - recoil calculator.Old Car Cost Calculator - Calculate and compare the costs between owning a new vs. Car Fuel Consumption - liter/100 km - Calculate fuel consumption in liter per km - consumption chart and calculator.Car Acceleration - Car acceleration calculator.Car - Required Power and Torque - Power, torque, efficiency and wheel force acting on a car.Bollard Forces - Friction, load and effort forces acting in ropes turned around bollards.Dynamics - Motion - velocity and acceleration, forces and torque.In metric units - person with weight 90 kg, falling distance 1.2 m and impact distance 2 cm: The impact on a human body can be difficult to determine since it depends on how the body hits the ground - which part of the body, the angle of the body and/or if hands are used to protect the body and so on.įor this example we use an impact distance of 3/4 inch (0.0625 ft) to calculate the impact force: The energy of the falling body when it hits the ground can be calculated using (4) as Note! - a car crash in 90 km/h (25 m/s) compares to a fall from 32 m!! Example - a Person falling from a TableĪ person with weight (gravitational force) of 200 lbs (lb f) falls from a 4 feet high table. The front impacts 0.5 m (slow down distance) as above. The same car as above falls from height 14.2 m and crashes on the crumple zone with the front down on a massive concrete tarmac. S = m a g h / F avg (5c) Example - a Falling Car The deformation slow-down distance can be expressed as If the dynamic energy from the fall is converted to impact work - equation 2 and 4 can be combined to The dynamic energy in a falling object at the impact moment when it hits the ground can be calculated asį weight = force due to gravity - or weight (N, lb f)Ī g = acceleration of gravity (9.81 m/s 2, 32.17405 ft/s 2) For a car crash with 90 km/h (25 m/s) the de-acceleration will be 64 times gravity (same parameters as above). Note that the National Highway Traffic Safety Administration (NHTSA) states that 'the maximum chest acceleration shall not exceed 60 times gravity for time periods longer than 3 milliseconds'. The impact creates a force 28 times gravity!!Ī person sitting inside the car with seat belts on will de-accelerate with a force 28 times gravity. Note that the gravitation force (weight) acting on the car is only The front of the car impacts 0.5 m (the deformation distance).į max = 1/2 (2000 kg) (16.7 m/s) 2 / (0.5 m) Example - Car CrashĪ car with a mass of 2000 kg drives with speed 60 km/h (16.7 m/s) before it crashes into a massive concrete wall. Note! - The deformation slow-down distance is very important and the key to limit the forces acting on passengers in a car crash. The deformation slow-down distance can be calculated as The average impact force can be calculated as In a car crash the dynamic energy is converted to work and equation 1 and 2 can be combined to In an impact where the object is not deformed - the work made by the impact force slowing down the moving object equals to the work done by a spring force - and can be expressed asį max = maximum force at the end of the deformation (N, lb f)

When a crumple zone deforms in a car crash the average impact force is designed to be as constant as possible. S = deformation distance, crumple zone (m, ft) In an impact - like a car crash - the work made by the impact force slowing down an moving object over a distance by deforming the crumple zone can be expressed asį avg = average impact force during deformation (N, lb f) The dynamic kinetic energy of a moving object, like a falling ball or a driving car, can be expressed as

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