Unit 1: Kepler's and Newton's Laws: Mastery Test

Match the following points in a planet's orbit with their corresponding speeds.

• Aphhelion

• slowest

• Perihelion

• average

• Throughout the orbit

• fastest

• Equidistant from Sun

• constant

Answer explanation

Kepler's laws state that a planet moves fastest at perihelion, the closest point to the Sun, due to the stronger gravitational pull. Thus, the correct answer is 'fastest'.

Tags

NGSS.MS-ESS1-2

Which sentence in the passage describes retrograde motion of a planet?

• The planet appears to move westward for a short period.

• The planet moves in a circular orbit around the sun.

• The planet's speed increases as it approaches the sun.

• The planet is always visible in the night sky.

Answer explanation

The correct choice describes retrograde motion, where a planet appears to move westward for a short period, contrasting with its usual eastward motion. This phenomenon occurs due to the relative positions and movements of Earth and the planet.

Tags

NGSS.MS-ESS1-2

What is the apparent backward motion of Mars in the night sky known as?

• retrograde motion

• prograde motion

• introgade motion

• reversal motion

Answer explanation

The apparent backward motion of Mars in the night sky is called retrograde motion. This occurs when Earth passes Mars in its orbit, making Mars appear to move in the opposite direction against the background stars.

Select the correct answer. How can Kepler’s third law be expressed mathematically?

• T² = R³

• F = ma

• w = mg

• F = Gm₁m₂/R²

Answer explanation

Kepler's third law states that the square of the orbital period (T) of a planet is directly proportional to the cube of the semi-major axis (R) of its orbit. This is mathematically expressed as T² = R³, making it the correct choice.

Tags

NGSS.HS-ESS1-4

NGSS.HS-PS2-4

Select the correct answer. According to Newton’s law of universal gravitation, what is the effect of gravity on two objects as the distance between them increases?

• The force of gravity increases.

• The force increases by twice the previous amount.

• There is no effect on the force of gravity.

• The force of gravity decreases.

Answer explanation

According to Newton's law of universal gravitation, as the distance between two objects increases, the force of gravity between them decreases. Therefore, the correct answer is that the force of gravity decreases.

Match the following historical figures with their contributions to Kepler's research.

• Formulated the laws of motion and universal gravitation

• Albert Einstein

• Improved the telescope and made astronomical observations

• Tycho Brahe

• Provided the observational data used by Kepler

• Galileo Galilei

• Developed the theory of relativity

• Isaac Newton

Answer explanation

Kepler's research was primarily based on the precise astronomical data collected by Tycho Brahe. Brahe's observations of planetary positions were crucial for Kepler to formulate his laws of planetary motion.

Select the correct answer. Which of Newton's laws states that "every action has an equal and opposite reaction"?

• first

• third

• second

• fourth

Answer explanation

Newton's third law states that for every action, there is an equal and opposite reaction. This means that forces always occur in pairs, making 'third' the correct answer.

Tags

NGSS.MS-PS2-1

Select the correct answer. According to Newton’s second law, how much force will be required to throw a plastic ball and an iron ball of the same size through the same distance?

• The iron ball will require lesser force than the plastic ball.

• The plastic ball will require lesser force than the iron ball.

• Both the balls will require the same force.

• The plastic ball will require more force than the iron ball.

Answer explanation

According to Newton's second law, force is proportional to mass. The iron ball, being denser, has more mass than the plastic ball. Therefore, the plastic ball will require lesser force to throw the same distance.

Tags

NGSS.MS-PS2-2

According to Kepler’s first law, the shape of a planet’s orbit around the Sun is (a)  

• circular
• polygonal
• elliptical
• random

Answer explanation

According to Kepler's first law, planets orbit the Sun in elliptical shapes, not circular or polygonal. This means that the distance between a planet and the Sun varies throughout its orbit, confirming that the correct answer is 'elliptical'.

The effect observed in a planet’s speed in its orbit as it travels away from the Sun is that it (a)   .

• increases
• remains same
• decreases
• unpredictable

Answer explanation

As a planet moves away from the Sun, the gravitational pull decreases, leading to a reduction in its orbital speed. Therefore, the correct answer is that the planet's speed in its orbit decreases.

Tags

NGSS.MS-ESS1-2

NGSS.MS-PS2-4