Frames of Reference 1) You are foolishly standing up in the back of your friend Billy Bob’s moving pickup truck. Your other friend Benny Joe is standing still on the sidewalk. Billy Bob gets the truck going at 25 m/s heading toward Benny Joe. You wind up and pitch a water balloon at Benny Joe from in back of the moving truck. If you can throw the balloon at 10 m/s how fast was the water balloon moving when it left your hand? Hint: Sketch the vectors.

2) Same scenario as problem 1 except that you are throwing the water balloon at Benny Joe after the truck has passed him and is now moving away.

3) Train A heads West at 180 km/h. Train B is heading East at 225 km/h. a) How fast is train A approaching train B? b) How fast is train B approaching train A? c) How fast is train A moving relative to an observer on the ground?

4) Two boats are racing in a river. The blue boat travels east at 26 m/s. The red boat travels east at 32 m/s. The water in the river is still. a) What is the velocity of the red boat relative to the blue boat? If you are having trouble picturing this question, imagine: If the blue boat were sitting still, how fast would the red boat appear to people on board the blue boat?

b) What is the velocity of the blue boat relative to the red boat? c) If the water in the river is moving west at 2 m/s does this change answer a) or b)? Explain. d) If an observer is riding a raft that is floating with the 2 m/s current, how fast does the blue boat appear to the observer as the boats race past?