Answer to Question #270906 in Mechanics | Relativity for Marshmallow

Question

Arlene is stationary relative to the ground. Aiza is riding toward A rlene on her e-bike 5 m/s relative to the ground. Aiza throws a water balloon forward at 3 m/s relative to the e-bike. With what speed does it strike Arlene? (Solution)

Answer 1

water balloon speed relative to the bike:

$v_1=v-v_2=5-v_2=3$ m/s

where $v$ is bike speed relative to the ground,

$v_2$  is water balloon speed relative to the ground

then water balloon strikes Arlene with speed:

$v_2=5-3=2$ m/s