- Published 18 Apr 2023
- Last Modified 29 Aug 2023
- 6 min
What is a Newton Meter?
A Newton meter or spring scale is a device for measuring the force of an object.
This guide will explain what Newton meters are, how they work, and what they can be used for.
History of the Newton Meter
The measurement of force and the measuring tool itself is named after the physicist Isaac Newton, best known for discovering gravity and his three laws of motion. He also contributed to calculus and helped with the principles of light. What might be surprising to you is that he didn’t create the first Newton Meter. This instead was created by Richard Salter in the mid to late 1700s and was later patented in 1838, under his company name. Though an old technology, Newton meters still have a vital place in the modern world.
What Does a Newton Meter Measure?
Just as scales measure weight and tape measures show length, a Newton meter’s purpose is to measure force. It is also known to many as a spring scale or spring balance. Specifically, spring scales measure the force acting on an object, the unit of which is the Newton.
How Does a Newton Meter Work?
How do you use a spring balance? Well, how a Newton meter works is actually very simple. The top of a spring balance consists of a handle, which is connected to a spring, which is then connected to a hook. The spring is covered in a casing, which has measurements in Newtons all the way down the casing. The spring scale is hung from the handle, and an object is placed on the hook. The hook is then pulled down due to the weight of the object, which pulls on the spring and indicates the force in Newtons. It is important to note that this is not the same as measuring weight (measured in kg), as the purpose of the tool is to focus on the force applied to the spring, not the mass of the object.
Hooke’s Law is named after Robert Hooke (a physicist in the 1600s) and is a physics calculation for working out force. Hooke’s Law states that the measurement of force is proportional to the distance applied and the consistency in stiffness of the object, in this case, that is the spring. In mathematics, force is represented as F, consistency is represented as k and distance is represented as X. The equation for Hooke’s Law is shown as F=X.k. To summarise, when we are using a Newton meter, we are not focusing on the object attached, but we are actually focusing on how the mass of that object affects the force applied to the spring inside the Newton meter.
Newton meters come in a range of sizes and can measure force in objects with very small masses or objects with very large masses, up to around 5 tonnes of mass.
Why Does the Newton Meter Never Reach Zero?
In most cases of measurement, the starting point is zero. However, in the case of a Newton meter, it will never measure zero Newtons on an object. Why not? Not every object is moving or falling or being pushed. The answer to this is that there is always a force applied to an object. If an object is not moving or falling, this is not due to a lack of force, but equal forces on each side. To explain using an example, a helium balloon floats, not because there is no gravity applied to the balloon, but because the balloon weighs a lot less, so the resisting force is stronger. Going back to Newton meters, it will not show zero, because in our atmosphere there is always gravity or gravitational force. When we are measuring the force of an object on a Newton meter, it is the pull of the object we are measuring, and gravity is always pulling down on an object.
What is a Newton Meter Used for?
Newton meters have wide and varied uses, in a range of environments and industries. Their first use is in schools in education. They are often used in physics and science classes, when teaching the principles of force, and are a great solution for demonstrating such scientific principles as the effect is plain to see.
Though the measurement of force is not the same as measuring mass, some Newton meters come with a mass scale and they are used as a way to measure the weight of the object. In this instance, Newton meters can be seen in both industrial and commercial settings. Newton meters or spring scales can be seen in the fruit and veg aisle in most supermarkets and are used in agriculture for weighing large volumes of produce. They are also used in industrial settings for weighing heavy vehicles such as lorries or trucks.
Newton meters are great for weighing mass because their simplicity in design makes them a budget-friendly option for weighing large objects. Their disadvantage can be their accuracy. Newton meters are not conclusively accurate in their measurement of weight, due to the fact that their springs will weaken over time from the force continually exerted on them. However, where exact measurements are not pivotal, and a close approximation is sufficient, they are a very effective tool.
Newton Meter Conversion
Once the force of an object is known, we can also use this information to calculate the ‘work’ or ‘torque’ of an object and convert our force measurements to represent these calculations.
To first work out these measurements, we need to know what ‘work’ and ‘torque’ are. In physics terms ‘work’ means the amount of energy that is needed when 1lb is moved at a distance of 1ft, and this measurement is in units of ft-lb. There are plenty of calculators online that can convert Newtons into ft-lb and vice versa, but a good starting point is to know that 1 ft-lb is equal to 1.356 Newtons.
Torque is similar to work in that it is a measurement of force through distance and weight. Where it differs is that torque is one pound of force and one foot’s distance away from a pivoting point. So torque is the term used when force is used to turn, rather than push through. Torque is measured in lb-ft and 1 lb-ft is equal to 1.356 Newton Meters, which is also comparable to work.
