Peter Graves
From Wikipedia's page for the author: http://en.wikipedia.org/wiki/William_P%C3%A8ne_du_Bois 

Peter Graves (1950): A well-meaning but mischievous boy who encounters a gentlemanly and not-very-mad scientist named Houghton Furlong. Furlong is the inventor of an antigravity material named Furloy, and a Furloy-based invention called "the ball that bounces higher than the height from which you drop it." In an unfortunate accident with the latter invention, Peter destroys Houghton's house. Little of value is left in the wreckage except six balls of Furloy, each about the size of a tennis ball, with an antigravity pull of 25 pounds-force (110 newtons) each. Peter commits himself to spending the summer with Houghton in an attempt to earn the $45,000 necessary to rebuild his house. The implied puzzle is: how can Peter and Houghton make use of the six Furloy balls to earn $45,000?
Children's stories, Juvenile Fiction, Science Fiction, Gravitation, fiction, Children's fiction
William Pène Du Bois
William Sherman Pène du Bois[a] (May 9, 1916 – February 5, 1993) was an American writer and illustrator of books for young readers. He is best known for The Twenty-One Balloons, published in April 1947 by Viking Press, for which he won the 1948 Newbery Medal. He was twice a runner-up for the Caldecott Medal for illustrating books written by others, and the two Caldecott Honor picture books, which he also wrote.
[source](https://en.wikipedia.org/wiki/William_P%C3%A8ne_du_Bois)