Radial force is a force that is exerted perpendicular to the centerline, or axis, of an object. The force along the axis is known as an axial force. Radial forces are typically measured in pounds (lbs) or Newtons (N). This plays a role in many physics and machine design applications.

This energy is necessary to make a mass travel in a circular orbit. When a known mass spins around in a circle of a certain radius, at a fixed speed, the radial force will act on the mass in a direction outward from the center of the circle, along the radius. This force keeps the mass spinning at the fixed distance from the center point.

For example, a cutting tool experiences radial force when it removes material while machining a part or surface. The force will act on the cutting tool in a direction perpendicular to the direction of the depth of cut. The amount of force acting on the cutting tool will depend on the tool features, and properties of the material being machined. The type of cutting tool, and rate at which the tool removes material, must be selected to ensure the radial force is minimized, and quality of the machined surface meets specifications.

Radial force also plays an important role in the usable life of a bearing. Bearings are widely used in many different types equipment to support, guide, and reduce the friction of motion between fixed and moving machine parts. Bearings are often exposed to radial forces that create internal material stresses, and complete failure if the force is high enough and the stress becomes excessive. There are different types of bearings, some of which are designed specifically for mechanical applications, on which high radial forces will be applied.

A momentum that is changing or evolving is known as radial force variation, which can be illustrated using the example of an automobile tire. The tire will experience a radial force applied by the road in a direction perpendicular to the axel of the wheel. This is constant for a tire that is perfectly round, and is spinning on a perfectly smooth road surface. In reality, a tire is not perfectly round because the tire's surface wears unevenly over time; the properties of the rubber may not be uniform; and a road surface usually has many bumps. As a result, the radial force of an automobile tire will vary with each rotation.