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# ZingPath: Gravity and Motion

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## Gravity and Motion

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### Lesson Focus

#### Escape Velocity: Launching Rockets

Physical Science

In this science fiction adventure, you will attempt to launch rockets and discover the relationship between escape velocity and a planet’s mass.

### Now You Know

After completing this tutorial, you will be able to complete the following:

• Define escape velocity as the minimum velocity required to break away from a planet’s gravitational pull.
• Explain that the larger the mass of a planet, the more its gravitational pull for objects at the same distance.
• Explain that escape velocity is directly proportional to a planet’s mass.

### Everything You'll Have Covered

Gravitational pull may be defined as the attractive force between two bodies which is directly proportional to their masses and indirectly proportional to the distance between them. We have observed that objects that have a bigger mass produce a stronger gravitational pull than smaller ones. We have also observed that escape velocity is the minimum velocity required to break away from a planet's gravitational pull. If an object is launched with a velocity that is equal to or greater than a planet's escape velocity, the object will break free from the planet. The escape velocity depends on the planet's gravitational pull. The greater the gravitational pull, the greater the velocity must be to escape the planet. The planet's gravitational pull depends on its mass. A planet with a larger mass has more gravity. Therefore, the escape velocity depends on the planet's mass. The escape velocity is directly proportional to the planet's mass.

Russia put this knowledge to work and hurled our planet into the space age in October 1957. Soviet satellite, Sputnik 1, was the first artificial satellite to orbit the Earth. It weighed only 83.6 kg or 183.9 pounds and was about the size of a basketball. Its elliptical orbit around the Earth took about 98 minutes. Americans from coast to coast gazed into the sky with great trepidation as Soviet Sputnik passed overhead. Russia followed up a month later with Sputnik 2, which carried Laika the dog into orbit. America's response in 1958 was to launch Explorer 1, a satellite that carried a small scientific payload and discovered the magnetic radiation belts around the Earth. That same year, The United States created the National Aeronautics and Space Administration, NASA, and invited some of the world's best scientific minds to help America not only to keep pace with the Soviets but to surpass them. Rocket clubs and competitions sprang up around the United States, and young people were challenged to become amateur aerospace engineers, developing new rocket technology, even if it was on a miniature scale.

Clearly, the space race was on. For the Soviet Union and America alike, this was a matter of national security and national pride. Russian Yuri Gargarin became the first human in space in 1961. America answered by sending Alan Shepard into space that same year for a short flight and by securing John Glenn's title as the first American to orbit the Earth in 1962. America won a major battle on the space front when Apollo 11 carried Neil Armstrong, Buzz Aldrin, and Michael Collins to the moon in 1969. Some say the space race ended when American Apollo 18 and Russian Soyuz 19 linked in space. Although there may have been a new spirit of cooperation between the two superpowers, each continued to pursue advancement in their own space programs. To this end, the United States launched the world's first reusable spacecraft in 1981 when space shuttle Columbia left Earth. NASA put the Hubble Space Telescope into orbit in 1990, and it has allowed us to gaze deeper into space than ever before. The James Webb Space Telescope will replace Hubble. Its launch is planned for 2013, and it is expected to deliver to us amazing images never before seen by the human eye.

### Tutorial Details

 Approximate Time 20 Minutes Pre-requisite Concepts Students should be familiar with the concept of gravity. Course Physical Science Type of Tutorial Concept Development Key Vocabulary alien, escape velocity, gravitational pull