What is the Impact Force on Different Objects?

two goats colliding heads

All around us, different invisible forces are coming together to control our natural environment. For example, gravitational force is the attraction between objects with mass, and it’s what keeps us on the ground instead of floating out to space. Then, there’s electromagnetism, which is when an electric current produces a magnetic field, and it’s what allows us to utilize electricity, generators, and electric motors. These concepts all fall under the study of physics, but even if you’re not a physicist, just knowing some of the basics of the field can help you better understand the world around you.

One physics concept in particular that you’re sure to come across on a regular basis is impact force. If you’ve ever thought about the impact of a car when it crashes, a plate when it drops to the floor, your phone when it falls to the ground, a ball when it hits you during a sports game, or any other situation where two things collide, then you’ve been exposed to impact force.

Here are some interesting facts about impact force as well as how you can calculate an approximate average level of impact force with an impact force calculator.

What is Impact Force?

To put it in its simplest terms, impact force is the force created when two or more things collide. This collision could be one object crashing into another object, or it could be as simple as one body of mass falling and hitting the ground. During a collision like this, kinetic energy transfers from one object to another.

The units for measuring force are Newtons, which are abbreviated as “N.” You may also see variations of Newtons like kilonewton (kN) or meganewton (MN). When measuring the force of impact, you can look at the average impact force, which is the average amount of force over the assigned time period of a collision. You can also measure peak impact force, which is the maximum impact force during the collision.

The Impact Force on Different Objects

There are many variables that go into determining impact force and these parameters go into the formulas for calculating the impact force. That’s why even if you’re looking at multiple examples with the same object – say, a standard size soccer ball – the ball isn’t necessarily going to have the same impact force in every scenario. To calculate the impact force you need to know:

  • Body’s mass: How much the body or object weighs.
  • Velocity on impact: How fast the body or object was moving on impact.
  • Collision/impact duration: How long the two bodies of mass are in contact.
  • Collision distance: How much the body gives in during the collision.

For instance, the power of an object’s impact force increases the faster the object is going. Just think: If you’re driving a car at 5 mph and hit a tree, you’re not going to do as much damage as you would if you were driving at 50 mph.

blue car with front damage from collision

How to Calculate Impact Force

While there is a mathematical formula that allows you to figure out impact force, those who aren’t particularly math or science-inclined might find it easier to use a simple, online impact force calculator to get their questions answered.

Using GIGACalculator’s tool, you can plug in the mass of the object or body, the velocity at which the object is moving upon impact, collision distance, and impact duration. Once you’ve input all of your information and hit “calculate,” you’ll get an average impact force and a peak impact force measured in Newtons.

Playing around with this tool, you can see how increasing the velocity can dramatically increase the impact force. Alternatively, you can see how increasing the collision distance significantly decreases the impact force.

Impact Force on Humans

Since impact force can affect any two objects, the human body isn’t exempt from its effect. But just how much impact force can humans take? 

It may not be pleasant to think about, but one way of looking at this question is to consider how much force our bones can take, or how strong the impact has to be to break a bone. On average, it takes about 4,000 newtons to break a typical human femur, which is the toughest bone in the body. That being said, there are other factors to consider too, such as the angle the “blow”comes from as well as how healthy a person and their bones are.

How to Reduce the Impact Severity

One way to reduce impact force is to lengthen how long the collision is. Extending the time of a collision means adding more deceleration time. This, in turn, means that the impact force’s effect on an object is minimized. For the mathematically inclined, the above is evident by examining the impact force calculation formula. Since time is in the denominator, increasing it decreases the calculated force on impact.

To make things a little easier to under, let’s go to back to the car crash example. Cars have something called crumple zones or crush zones, which are the areas that can get crumpled or crushed during a collision to keep the people inside of the vehicle safer. If you were in a car without a crumple zone, that initial impact is felt sooner and much more of the kinetic energy of that collision would be transferred directly to you. On the other hand, if you’re in a car with a crumple zone, that area can take the brunt of the initial impact and lessen how much force you’ll feel.

Staying with the car crash scenario, airbags also work to lengthen a collision’s time by bringing passengers inside to a stop more slowly. Instead of a windshield stopping the person’s momentum in a short period of time, an airbag can slow this momentum over a longer period of time. Both of these examples may seem like minimal time differences, but they can have a huge impact on the kinds of injuries someone can sustain.

However, the biggest factor for reducing impact severity by far is reducing the velocity of the moving object. In the impact force formula the velocity is in the numerator and it is squared, so any increase in the velocity has an inordinate effect on the experienced crash force. In an example calculation, a car moving at 20 mph would impart a force on impact of 120 kN over a 0.5 meters impact distance whereas the same car would hit an object with 480 kN of force if moving with 40 mph (with the same impact distance). Twice the speed results in four times the force.

Impact force is a physics concept that can be seen all around us when two objects collide or when an object falls. Mass, velocity, and duration of collision are all factors that affect the impact force, and an impact force calculator can be used to estimate both the average impact force and peak impact force from a collision.

This entry was posted in Mathematics, Science and tagged , , , . By Cindy Brzostowski