Amodel airplane with mass 0.5 kg hangs from a rubber band with spring constant 45 n/m. how much is the rubber band stretched when the model airplane hangs motionless?

0.109 m (10.9 cm)

Explanation:

The weight of the airplane hanging from the rubber band is given by the product between its mass (0.5 kg) and the acceleration due to gravity (g=9.8 m/s^2):

This is the force that stretches the rubber band, according to Hook's law:

where

k = 45 N/m is the spring constant

x is the stretching of the spring with respect to its equilibrium position

Substituting F = 4.9 N and re-arranging the formula, we get: