"Plays Ball" is the tenth episode of season one of the animated children's series The Magic School Bus. It originally aired on November 12th, 1994.
Dorothy Ann has brought a book about physics to school, but everyone else thinks it's boring. Ralphie borrows it from her to use it as a replacement for home plate. She doesn't learn of this until they set off on a field trip. Ms. Frizzle decides to back up and get the book, but the bus shrinks and lands on page 97 which has a frictionless baseball field. The class soon learns that friction is needed for the simplest actions, from playing baseball to walking. However, when they are about to leave, the wind blows the book shut, trapping everyone inside. Ralphie and D.A. have to put aside their argument in order to work together and get the bus unstuck.
At the local baseball stadium, Ralphie is seen batting and the audience cheer him on from the bleachers. Just then, Keesha's voice is heard, and Ralphie is revealed to have fantasized the whole scenario. He is next to bat at the batting cage at the park with the other students and notices that there is no home plate, for the students are pretending. Wanda is on the pitcher's mound and pitches the ball to Ralphie. But the game is interrupted by Dorothy Ann, who shows them a book of physics. As Liz runs into the classroom's window, Dorothy Ann tells the other students about her book and the others scoff at this. Ralphie attempts to shew Dorothy Ann off the field. But Dorothy Ann explains that the book is about what makes things move and what makes them stop: forces frictions, pushes, and pulls.
Ms. Frizzle overhears the students' conversation and decides to implement a field trip. During the conversation, the students continue to mock Dorothy Ann's affinity for physics, telling her that if she's going to "force" them to listen, she's being kind of "pushy". Dorothy Ann then uses an analogy and tells them to picture a big, red sled in a snow that is stationery until someone hops onto it and Napoleon (as Arnold states since he needs to know who pushes the sled to refresh his memory) gives it a push to elicit its motion, thus creating a force. The sled would continue to move until something stops it, such as dirt, thus creating friction, which slows down and stops every motion on earth. The students, however, are more than apathetic of this and continue their game. But when Ralphie rubs his bat against the dirt, he changes his mind and gains interest in the book. Dorothy Ann then shows him a page of the baseball field and tells him that it would be impossible to play normal baseball there. Ralphie asks Dorothy Ann if he could borrow the book, to which Dorothy Ann agrees, telling him to promise to take good care of it. Just then, the magic school bus arrives and gives the students a ride for a field trip.
The field trip is to a baseball game, much to the students' delight. Dorothy Ann, however, is less than thrilled about this and decides to go to the baseball diamond, like the one she showed Ralphie on page 97 in her book of physics. Ralphie soon remembers that he had dropped the book on the ground back at the baseball field at the park and Ms. Frizzle shrinks the bus in size to turn to page 97, which shows the picture of the baseball diamond. Once there, Dorothy Ann explains that the page is about a world without friction and Ralphie exits the bus to get to the page, only to find that the grid on the bus is devoid of friction.
Ralphie continues to bounce on and off the walls of the grid, and Carlos calls him "Ralphie the Runaway Pinball". The students follow along and slide through the grid as well. Dorothy Ann ends up pushing herself against Ralphie as the two collide, resulting into a complete stop. Ralphie then pushes Dorothy Ann and they continue sliding as Carlos jokingly tells Dorothy Ann that Ralphie gave her the "push-off". Ms. Frizzle then offers the class baseball gloves and has Liz transform the bus into a blimp, sending it floating overhead. The students are hoisted into their positions in the friction-free baseball diamond and Ms. Frizzle and Dorothy Ann announce the game. They report the loss of friction around the field, where the others have a hard time standing up. Wanda is the pitcher, Arnold is the catcher, and Ralphie is up to bat. Wanda pitches the ball and is pushed backwards. Arnold catches the ball and is pushed into Ms. Frizzle, who pushes him back to the catcher's position. He tosses the ball back to Wanda and Wanda pitches the second time. Ralphie hits the ball and the force of his swing causes him to spin out around the frictionless field. Carlos catches the bouncing ball, which sends him backwards, and Wanda bumps into Tim as well. Ralphie continues to spin around the field until he finally makes it to home and ends up colliding against Dorothy Ann once again, and the two spin together. Dorothy Ann decides to call off the game due to lack of friction and the students continue to slide around the grid. Liz pops the blimp on top of the bus, which lands onto the page. The bus ejects a piece of string out and the students grab onto it, with Ralphie and Dorothy Ann, who are still sliding together, arguing. The others use their hands to pull themselves to the bus and Ralphie and Dorothy Ann follow suit.
The students acknowledge their interest of the book to Dorothy Ann and everyone hops onto the bus. But a gust of wind outside blows the pages of the book onto the bus. So Ms. Frizzle steps on the gas pedal to use enough force to propel the bus out of the book. But the cover of the book has just about enough friction to keep the bus stuck inside, and the bus finally gives in.
When the bus still struggles to get out, Carlos jokingly states that the others "will be food for the bookworms", as well as stating "a real heavy situation". So Ms. Frizzle exits the bus, saying "those who are book bound should take a look around". As the students exit the bus, they learn that there isn't enough friction below for the wheels to propel and that there is too much friction above the bus. Carlos tells the others that they are somewhere between pages 96 and 97, adding that he is "just trying to lighten things up", indicting an idea. The students should get onto the book, hold it up, and drive out of it. When Ralphie kicks one of the letters out of the pages out of anger, Dorothy Ann decides that the students should split up to two teams: Ralphie's team goes on the roof and pushes up on the book while Dorothy Ann's team puts down letters to hold up the book. Ralphie and Dorothy Ann begin arguing again over which team should do what, and Arnold reminds them that in order to escape the book, the two should "get rid of the friction between them". So Ralphie and Dorothy Ann apologize to each other and argue over who's more sorry.
When the students finally get the job done, they enter the bus and Ms. Frizzle propels it out of the book and transforms it to its normal size. The students continue their game at the baseball diamond and Dorothy Ann is next to bat. Wanda pitches the ball to her and Dorothy Ann hits a home run. The students then notice that the plate is missing and they find Ralphie reading the book, which he has suddenly gain interest to. Ms. Frizzle comes to a conclusion, stating "Never judge a book by its cover", causing the students to laugh.