Forces in Car Crashes

Index

Work-energy principle

Example of Force on Car

(This initial example is cast in U.S. common units because most U.S. readers can make comparisons to known forces more easily in those terms. The calculation provides the results in SI units as well.)

Note: these examples of forces during collisions use the average of force over distance rather than the average over time. The profile of force during a collision such as that of a car with a tree can be complex, whether expressed in terms of time or distance. The average over distance is used here because of its relationship to the conservation of energy and the work-energy principle.

Index

Work-energy principle

Calculation of Force on Car

If the weight of the car is N = lb, corresponding to
mass = kg = slugs,
and the car is traveling with a speed:
v = m/s = km/hr = mi/hr,
then a crash which stopped the car in a distance d=m = ft
would result in an average impact force of

Impact force F = N = lb = tons!!

You may change any data value. Clicking outside the box will then initiate a calculation of the impact force and conversion of the data value to the other types of units. Index

Work-energy principle