Karen is running forward at a speed of 9 m/s. she tosses her sweaty headband backward at a speed of 20 m/s. the speed of the headband, to the nearest whole number relative to a stationary observer watching karen

The speed of the headband, to the nearest whole number relative to a stationary observer watching Karen, is 11m/s

Explanation:

The velocity of the headband relative to the stationary observer is equal to the velocity of Karen relative to the stationary observer plus the velocity of the headband relative to Karen. Mathematically:

Where:

(it's negative because it mover backward)

: velocity of the headband relative to the stationary observer

Plugging these values

Speed is simply the magnitude of velocity or its absolute value, that is to say, 11m/s (positive)