Ball being shot backwards off a moving vehicle? Relative motion? A truck travelling at 80 km/h has a pitching machine firing baseballs backwards off the back. The pitching machine is set to fire at 80 km/h. a) how does a passenger in the truck see the ball move? b) how does a person at the side of the road see the ball move? **attempt** a) since the ball is going -80km/h [forward] and the truck is going 80km/h [forward] would the ball appear "not moving"?? b) the person at the side of the road sees the ball going downwards, or south?

To the passenger the ball appears to be moving at 80 kph backwards. The ball is fired relative to his frame of reference, so the fact that the truck is moving is irrelevant.

To a person at the side of the road it looks like the ball is stationary -- it will fall straight down according to gravity. The forward motion of the truck and the backwards speed of the pitch exactly cancel each other out.