The person walked slowest when going up some steps. Complete the sentence. Choose the answer from the box.
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When walking up the steps, the person did more work against the force of __________.

Work is done when a force moves an object through a distance (Work done = Force × distance). - **Air resistance** and **friction** are forces that oppose the person's forward motion. - **Gravity** is the force that pulls the person's mass downwards. When walking up steps, the person has to lift their body vertically against the force of gravity. This requires doing work against gravity, in addition to the work done against friction and air resistance.