posted by Shandy .
Bob is roller-skating at a speed of 1.5 m/s relative to the ground. He tossed a small ball forward. The ball moves at a speed of 1 m/s relative to Bob. What is the speed of the ball relative to the ground?
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Velocity-addition formula gives
v= 1.5 +1 = 2.5 m/s
Elena is right but, why to make a physics question in the foreign language subject?