In the equation m g − T = m a, what does the right-hand side m a represent?

• A. Mass times velocity.
• B. Gravitational force.
• C. Net force on the mass.
• D. Tension.

Answer: (C)

The right-hand side represents the net force on the mass, which, by Newton’s second law, equals mass times acceleration. In this setup, gravity (mg) pulls downward and tension (T) pulls upward, so the sum of forces along the vertical is mg − T, and that net force produces the acceleration a in the same direction. This isn’t just gravity or tension by themselves; it’s the combined effect of all forces acting on the mass. If mg > T, the net force is downward and the mass accelerates downward; if T = mg, the net force is zero and the mass doesn’t accelerate.