Physics

Physics

Problem

An elevator of mass 900 kg900\,\text{kg} is moving upward at constant velocity through the air. External forces on the elevator are its weight W⃗\vec W, an upward tension T⃗\vec T from the cable, and a downward air-resistance force R⃗\vec R of magnitude 1.8×103 N1.8\times10^{3}\,\text{N}. Write the quantitative relationship these forces must satisfy for translational equilibrium and determine the numerical value of the tension TT.
Intuitive explanation

When an object moves at constant velocity, its acceleration is zero—so the net force must be zero. This is translational equilibrium, and it means all forces must balance. Here, you have three vertical forces: weight (down), tension (up), and air resistance (down). Set up the equilibrium equation by making up positive, then solve for the unknown tension using the given mass and resistance.

Intuitive explanation

When an object moves at constant velocity, its acceleration is zero—so the net force must be zero. This is translational equilibrium, and it means all forces must balance. Here, you have three vertical forces: weight (down), tension (up), and air resistance (down). Set up the equilibrium equation by making up positive, then solve for the unknown tension using the given mass and resistance.

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