Master the Laws of Gravity

Isaac Newton's Law of Universal Gravitation and Kepler's Three Laws

• Newton's understanding of gravity was a major contribution to physics.
• Before Newton, scientists had little concept of gravity.
• Newton's realization that gravity affected the apple and the Moon led him to investigate further.
• Newton developed an equation to describe the way gravitational force made objects behave, called the law of universal gravitation.
• The law of universal gravitation states that the gravitational force between two objects is proportional to the mass of the two objects multiplied together and divided by the square of the distance between them.
• Newton added a constant to his equation, called G, to make the gravitational force just a tiny fraction of what you'd calculate otherwise.
• Henry Cavendish measured G to be about 6.67 * 10^-11 N*m^2/kg^2.
• Newton's law of universal gravitation fit with Kepler's three laws of orbital motion.
• Kepler's first law states that the orbits of planets are ellipses with the Sun at one focus.
• Kepler's second law states that a planet sweeps out equal areas in equal times.
• Kepler's third law states that the ratio of the cube of a planet's semimajor radius to the square of its period is the same for every planet.
• NASA still uses Newton's math to calculate gravitational acceleration and test spacesuits for Mars missions.

Test your knowledge of Isaac Newton's Law of Universal Gravitation and Kepler's Three Laws with this quiz! Learn about Newton's contribution to the understanding of gravity, his equation for gravitational force, and how it fits with Kepler's laws of orbital motion. See if you can answer questions about the laws and their applications, including NASA's use of Newton's math for Mars missions.