By newton's Third law of Motion, every action has an equal and opposite reaction, the astronaut would be thrown back. The tennis ball would however keep on going in the direction until another force acted upon it(planet's gravity, meteor, etc.) by Newton's Third Law
Assuming there were no large celestial bodies, like the earth or sun, near by to capture the object in its gravitational field, the lack of friction in the vacuum of space would allow any object thrown to travel at the same speed indefinitely, or until it came in contact with another object.
Consequently, if an astronaut threw an object in space without standing on something like a space station or space ship, according to Newton's third law, he would tumble, or spin in a circle because of the equal, opposite force exerted upon him by the thrown object, as well as the rotation of the astronauts arm used to throw the object.
an astronaut
Ask a astronaut....
Astronaut Goes from Migrant Fields to Outer Space - 2010 was released on: USA: 7 April 2010 (Southeast New England Film, Music & Arts Festival)
Cosmenauts
The Americans went first in space if manned it was in 1961 and Alan. B. Shepherd was the astronaut.
In weightlessness, an astronaut that "pretends" to throw an object may find his or her arm's sudden movement causes their body to rotate in the same direction. If they actually threw a mass, the forces would cause the astronaut to travel in the opposite direction.
an astronaut
An astronaut needs a space suit that will allow him or her to stay safe in zero gravity. The astronaut also needs a camera that will record images from outer space.
Alan sheperd was the first astronaut in space.
Astronaut
An astronaut in outer space
Black
The rock will move at the same speed it was thrown forever until it hits something else or is affected by another objects gravity. in theory if it passes no large objects and hits nothing it may go on forever at the same speed
An astronaut.
yes
An astronaut in outer space
The cast of Astronaut Goes from Migrant Fields to Outer Space - 2010 includes: David Moolten