Based on reports by the Bureau of Labor Statistics, one person gets injured by a falling object in their workplace every ten minutes. That’s about 50 thousand reported cases every year.
These incidents are most common in workplaces where work at height is done. In work at height areas, the most common objects that fall and cause injuries are handheld tools and material debris.
The range of damage or injury can vary from a slight bump to a crack in the skull. The possible victim’s safety depends on the object’s mass, the height of the fall, and the acceleration due to gravity. These physical elements determine the impact force that can cause damage.
How? The following section will explain.
The Physics of Falling Objects
Although keeping a hard hat on at all times may keep you generally safe from a direct hit, not all falling objects have the same impact force. Thus, you can still incur concussions and contusions in spite of the hard hat. But how exactly can falling objects cause such damage from a certain height?
According to physics, when an object at rest suddenly falls, the force of gravity converts its potential energy to kinetic energy—energy in motion. Gravitational pull causes the object to accelerate and creates force. This force is what generates impact when the object hits or collides with something after falling.
To calculate an object’s impact force when it falls from a certain height, you first need to calculate how much kinetic energy the object had before the point of impact. You can do that using the following equation:
E = mgh
E stands for energy, m for object’s mass, g for acceleration due to gravity (constant is 9.81 m/s-2), and h for the falling height.
To incorporate this equation into solving the average impact force of the falling object, you need to take into account the distance traveled by the object.
The distance traveled does not automatically equate to the falling height. This is because the falling height is the distance of the point of fall from the ground, whereas distance traveled is the distance the object traveled when it hits the ground before stopping completely.
To get the average impact force (in Newtons), you’ll need this equation:
Average impact force = mgh / d
Or
Average impact force = E / d
E or mgh stands for the change in kinetic energy and d is for distance traveled by the falling object.
For this calculation, the height and distance should be in meters, and the weight should be in kilograms.
Now, for example, to calculate the impact force of a 3-kilogram wrench that falls from a 3-meter scaffold and embeds itself 5 cm deep into the ground, you’ll apply the formula as:
Average impact force = mgh / d
Average impact force = (3 kg * 9.81 m/s-2 * 3 m) / 0.05 m
Average impact force = 88.29 / 0.05 m
Average impact force = 1765.8 or 1766 Newtons
This result means that it takes a force of 1766 Newtons for a 3-kilogram wrench to penetrate the ground 5 cm deep after falling from a height of 3 meters. Without head protection, this amount of force is enough to knock someone unconscious and cause a skull fracture. In some studies, it has been proven that a force of 2300 Newtons is enough to crush a skull in one hit.
Preparing for and Preventing Damage from Falling Tools
Once you get how the formula works, you can calculate the impact force of any falling tool or object in your workplace. Knowing the physics behind falling objects can give you the following advantages:
It will provide you with an idea of how dangerous your tools can be when they’re dropped.
Knowing about the impact force of falling tools can help you plan for better safety measures in your workplace. This will help strengthen the workers’ awareness about the potential dangers of falling tools. It will also reinforce your company’s safety policies, particularly your tool tethering policy.
You can involve your workers in demonstrating how each tool can inflict injuries when dropped from heights. That way, they’ll know what can happen if they don’t tether or secure their tools when working at height. It’ll also prove to them that non-compliance should be treated as a grave offense.
It can help you estimate the extent of damage falling tools can cause.
When you know how much force your tools can have when they fall off a height, you’ll be better able to estimate how much damage they can cause. This can help you create mitigation plans for all the equipment and materials used in your work site.
By preparing for the possibilities of falling tools and objects in your workplace, you can better prevent injury and damage. You don’t need to master every physics principle, but having a clear idea of what impact force means can help you provide a safer workplace for everyone.