Question

question 20 (multiple choice worth 1 points)
os5.03when a spacecraft travels towards earth, the gravitational force acting on it

• increases
• decreases
• increases first and then decreases
• decreases first and then increases

question 21 (multiple choice worth 1 points)
os5.01which of these models of the solar system first proved that the sun is at the center of the solar system?

• ptolemy’s geocentric model
• brahe view of the solar system
• kepler view of the solar system
• copernican heliocentric model

Explanation:

Question 20

The gravitational force between two objects is given by \( F = G\frac{Mm}{r^{2}} \), where \( G \) is the gravitational constant, \( M \) and \( m \) are the masses of the two objects, and \( r \) is the distance between their centers. When a spacecraft travels towards Earth, the distance \( r \) between the spacecraft and Earth decreases. Since the gravitational force is inversely proportional to the square of the distance (\( F \propto \frac{1}{r^{2}} \)), as \( r \) decreases, the gravitational force acting on the spacecraft increases.

• Ptolemy’s geocentric model proposed that Earth was at the center of the solar system, so this is incorrect.
• Brahe’s view of the solar system was a hybrid model that still had Earth at the center (with some modifications), so this is incorrect.
• Kepler’s view of the solar system built on the heliocentric model and focused on planetary orbits (elliptical), but he was not the first to propose the sun - centered model.
• Copernicus’ heliocentric model was the first to propose (and provide a mathematical basis for) the idea that the sun is at the center of the solar system, with planets (including Earth) orbiting around it.

Answer:

A. increases

Question 21