Question

in which scenario is an animal doing work? check all that apply.
a cat lifts up her kitten by its neck.
a dog rubs his back against a large tree.
a bird flies a worm from the ground to its nest in a tree
a goat butts its head against the barn wall.
a horse pulls a wagon along a road.

Explanation:

To determine when an animal does work, we use the physics definition of work: \( W = F \cdot d \cdot \cos(\theta) \), where a force (\( F \)) causes displacement (\( d \)) in the force’s direction (\( \theta = 0^\circ, \cos(\theta)=1 \)).

• A: The cat applies an upward force to lift the kitten (displacement upward) → Work is done.
• B: The dog rubs against the tree, but the tree does not move (displacement \( d = 0 \)) → No work.
• C: The bird applies an upward force to move the worm upward (displacement upward) → Work is done.
• D: The goat pushes the barn wall, but the wall does not move (displacement \( d = 0 \)) → No work.
• E: The horse applies a forward force to pull the wagon forward (displacement forward) → Work is done.

Answer:

A. A cat lifts up her kitten by its neck,
C. A bird flies a worm from the ground to its nest in a tree,
E. A horse pulls a wagon along a road