Journal Entry 11/16

Let's pretend that observer A and B are at the site of the Japanese experiment with the baseball and the truck both moving at 100 km/h. Observer A saw the ball moving and observer B saw the ball not moving and here is the reason why...

Let's call person A: Jen and person B: Dan

Jen hears that her friends are doing a physics experiment at the local race track. She has finished all her homework, so she decides to head over to the track and check out the experiment. Her friend Billy who is in charge of the experiment tells her to take a seat in the stands while he and his friends perform the experiment. Billy and his friends start the car, and they drive it around the track. When it reaches 100 km/ hr, Billy shoots a baseball out of a pitching machine (which is also rotating it 100 km/hr). Jen is amazed by what she sees. The ball whizzes past her and she is truly impressed by Billy's experiment. (Jen's object of reference is the pitching machine)

Billy also told his best bud Dan about the experiment he was performing after school. Dan really wants to see what happens when the ball is shot out of the machine, while the car is moving, so he tries really hard to be on time. Dan forgets his driver's license at home after he leaves the house however, so he has to drive carefully back and get it. Behind schedule, Dan races to the track so that he doesn't miss the experiment. He drives the entire trip at 100 km/hr, even on some of the residential streets between his house and the track. Luckily he doesn't get a ticket. Although he's driving above the speed limit in an attempt to make it to the track on time, the experiment is being performed right as he passes the location. He watches the truck on the track, but the ball does not appear to be moving. After many moments of puzzlement, he realizes that because he is traveling at the same speed as the truck on the track, the ball doesn't appear to be moving. (Dan's object of reference is the truck)

Although a little surprising, both Jen and Dan are correct about the motion of the ball. Based on each of their positions and actions, the ball appears to have different motion. Jen is seated and her object of reference is the ball and the pitching machine. In terms of this machine, the ball is moving at 100 km/hr. Dan is driving pass the track at the same speed as the truck, and his point of reference is that truck. In terms of the truck, the ball does not appear to be moving.