Physics

Problem

A student burns about 300 food Calories during exercise. Assume

1\,\text{Cal}=4.2\,\text{kJ}

. If the student later pushes a lawn roller with a horizontal force of

200\,\text{N}

, the displacement required for the mechanical work done to equal the energy burned is closest to a)

6.3\text{ m}

3150\text{ m}

6300\text{ m}

630\text{ m}

Intuitive explanation

This problem connects metabolic energy to mechanical work—two different ways of measuring energy transfer. The key insight is that the work done by a force ( $W = F \cdot d$ ) must equal the total energy burned, so you're really solving for the displacement that makes the mechanical work output match the chemical energy input. Convert the food Calories to joules first, then use the work equation to find the distance.

Intuitive explanation

Browse the problem library