<h2>1. Right answer: the velocity of the spacecraft at position 2 is <u>greater than</u> the velocity of the craft at position 4.
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This is due the gravity field of the Earth is used to accelerate the craft. This is true when in a specific point the direction of the movement of the craft is the same direction of the movement of the planet.
In this case the craft will be “catched” by the Earth’s gravitational field, making the craft to enter a circular orbit.
<h2>2. Right answer: At point 1, the direction of the spacecraft changes because of <u>the gravitational force between earth and the spacecraft.
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As explained in the first answer, this is the exact point where the trajectory of the spacecraft enters into a circular orbit because of the attraction due gravity of the Earth and therefore changes its direction.
<h2>3. Right answer: Position 3 represents the <u>orbital path of Earth
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Being this the orbital path of the Earth and considering the trajectory of the craft, the condition of accelerating the craft is accomplished. If the orbital path of the Earth were the opposite from the shown in the figure, the effect on the craft would be <u>braking.
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Note all of these is related to the gravitational assistance, this consists in a maneuver in which the energy of the gravitational field of a planet or satellite is used to obtain an acceleration or braking of the probe or craft, changing its trajectory.
This maneuver is also called <em>slingshot effect</em>, swing-by or gravity assist.
