Page 466 - Canadian BC Science 9

Visualizing Rocket Motion
On the afternoon of July 16, 1969, Apollo 11 lifted off from Cape Kennedy, Florida, bound for the Moon. Eight days later, the spacecraft returned to Earth, splashing down safely in the Pacific Ocean. The motion of the spacecraft to the Moon and back is governed by Newton’s laws of motion.
Apollo 11 roars toward the Moon.
At launch, a rocket’s engines must produce enough force and acceleration to overcome the pull
of Earth’s gravity.
A rocket’s liftoff is an illustration of Newton’s third law: For every action there is an
equal and opposite reaction.
As Apollo rises, it burns fuel and ejects its rocket booster engines. This decreases its mass, and helps Apollo move faster. This is Newton’s second law in action: As mass decreases, acceleration can increase.
The lunar module uses other engines to slow
down and ease into a soft touch-down on the Moon. A day later, the same engines lift the lunar module again into outer space.
After the lunar module returns to Apollo, the rocket fires its engines to set it into motion toward Earth. The rocket then shuts off its engines, moving according to Newton’s first law. As it nears Earth, the rocket accelerates at an increasing rate because of Earth’s gravity.
448 MHR • Unit 4 Space Exploration
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