Question

• time required for the planet to make one ____________ around the sun.

+ law #3 example

• example: radius of the earths orbit, or its distance from the sun, is 1 au, and its period is 1 year.
• 1×1³ = 1² simplifies to 1 = 1.
• jupiter is 5.2 au from the sun and its period is 11.9 years. the cube of 5.2 = 140.6. the square of 11.9 = 141.6. 140.6 and 141.6 are approximately equal.
• the period __________ (p²) always equals the distance __________ (r³).

newtons application of keplers laws
+ isaac newton hypothesized that a moving body will change its motion only if an ____________ causes it to do so.

• the tendency of a moving body to move in a straight line at a constant speed until an outside force acts on it, is called ____________.
• also refers to the tendency of an object to remain at ____________ until an outside force acts on it.

+ because a planet doesnt follow a straight path, an outside force must cause it to ____________.

• newton called this ____________, the attractive force that exists between all objects in the universe.

+ the gravitational pull of the ____________ keeps the planets in orbit around the sun.

Explanation:

Kepler's third - law states that the square of the orbital period ($p^{2}$) of a planet is proportional to the cube of the semi - major axis of its orbit ($r^{3}$). Newton's first law is about inertia, which is the tendency of a moving body to move in a straight line at a constant speed or an object to remain at rest until an outside force acts on it. Since a planet doesn't move in a straight line, there must be an outside force, which Newton identified as gravity. The gravitational pull of the sun keeps the planets in orbit around it.

Answer:

• Time required for the planet to make one orbit around the sun.
• The period squared ($p^{2}$) always equals the distance cubed ($r^{3}$).
• Isaac Newton hypothesized that a moving body will change its motion only if an outside force causes it to do so.
• The tendency of a moving body to move in a straight line at a constant speed until an outside force acts on it, is called inertia.
• Also refers to the tendency of an object to remain at rest until an outside force acts on it.
• Because a planet doesn't follow a straight path, an outside force must cause it to curve.
• Newton called this gravity, the attractive force that exists between all objects in the universe.
• The gravitational pull of the sun keeps the planets in orbit around the sun.