Torque, Clarified

It is important to note that torque is not always determined by the total force applied on an object. Instead, it is only the force that is perpendicular to the lever arm that is taken into account in the calculation.

Buoyancy

 Buoyancy is the "tendency of a body to float or to rise when submerged in a fluid," (Merriam-Webster). This phenomenon is the result of the increasing pressure of fluids at increasing depths. According to Pascal's Principle, this pressure applies in all directions; therefore, the pressure on the bottom of glass balls pictured is larger than that applied by air on the top of the balls, causing a net upward force on them.

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.