The Universal Tug: Gravity and Orbital Motion Quiz

If a physical force is required to pull an object toward a center, and if the invisible force gravity acts as that pull between the Sun and the Earth, then gravity is the force keeping Earth in place.

If a planet is moving forward and gravity pulls it toward the Sun, then its path will bend into a curve; if this curve closes into a loop, then gravity has successfully held the planet in an orbit.

If an object is moving in a circle because of a constant pull, and if that pull is removed, then the object's inertia will make it continue in a straight line at its current speed.

If a planet travels a repeating circular or oval route around a star, then the technical term for that specific path is an orbit.

If gravity depends on mass and distance, and if an orbit is a balance of gravity and speed, then mass, speed, and distance are the core factors required to understand the motion.

If a planet moves too slowly, it falls into the star; if it moves too fast, it escapes; if it moves at just the right speed to balance the inward pull, then it stays in a stable orbital loop.

If every object with mass pulls on other objects, and if the Earth is much heavier than the Moon and nearby, then the Earth's gravity will pull the Moon into a curved path around it.

If gravity follows an inverse relationship with distance, then reducing the gap between two objects increases the attraction; if the gap increases, the pull becomes much weaker.

If the strength of gravity is directly related to how much "stuff" is in an object, and if mass is the measure of that stuff, then more mass results in a stronger pull.

If you swing a ball on a string, the string pulls the ball toward your hand to keep it in a circle; if gravity does the same thing to a planet, then the string is a perfect model for gravity.

If gravity is a field that travels through the vacuum of space, then it does not need air or a medium to exert a pull on a distant planet.

If mass exists everywhere, then gravity exists everywhere; if gravity is a pull, it curves motion; and if distance increases, the force weakens.

If the Earth were standing still, it would fall into the Sun; if the Earth is moving sideways at 67,000 miles per hour, then that speed creates the "outward" tendency that balances the "inward" pull.

If history records that a scientist linked the falling of an apple to the motion of the Moon, then that scientist is Isaac Newton.

If an orbit is a closed loop, and if we measure time based on one trip around that loop, then the result is the definition of a year.

If a planet moves faster, the inward pull of gravity is no longer strong enough to keep it in the same tight circle; if the speed is high enough, it will move further out or leave the system.

If Neptune is very far away, the Sun's pull is weak; if the pull is weak, the planet must move slower to stay in a stable orbit without being flung out or pulled in.

If gravity is a mutual force (Newton's Third Law), then every object pulls on every other object; if the Sun pulls on Earth, then Earth must also pull on the Sun.

If gravity is determined by mass, and if the Sun is the dominant source of gravity in the system, then it must contain almost all of the system's mass.

If a satellite is a smaller object moving around a larger mass, then it must follow the same physics of speed and gravitational pull that planets follow.