Motion Resistance

A spin performed by an ice skater is the result of more than just torque. Inertia, the skater's bodily resistance to a change in state also comes into effect by decreasing the speed of the skater. In situations such as making a turn while ice skating where the motion is rotational, this factor is called the "moment of inertia."

Law of Acceleration

Remember that Newton's first law stated that an object with no net force acting on it will not accelerate. Newton's second law of motion, though, states that an unbalanced force (one that is not equally opposed by another force) acting on an object will cause the object to accelerate. The object's mass, which measures its inertia, also determines how much the object's movement will change. From this, Newton derived the formula a= F/m, where acceleration is directly proportional to force and inversely proportional to object mass.