Gravity & Matter
Define matter in one sentence.
Matter: anything that has mass and takes up space (volume).
Define "mass" in one sentence.
Mass: a measure of how much matter is in an object.
What kind of force is gravity? (One-word answer.)
Gravity is an attraction force.
What keeps planets moving around the Sun instead of flying off in straight lines? (Name the force.)
Gravity (gravitational force from the Sun).
Name two examples of matter and two things that are not matter.
Examples of matter: rock, water. Not matter: light (energy), sound (energy).
Define "weight" in one sentence.
Weight: the force of gravity on an object.
List two factors that impact the strength of gravitational force between two objects.
Factors: masses of the objects; distance between them.
Briefly explain how inertia and gravity work together to make an orbit.
Inertia tries to make the planet move in a straight line; gravity pulls it inward; the balance creates a curved path (orbit).
Explain why air is considered matter even though you can't always see it.
Air has mass and occupies space; it exerts pressure and can be measured (e.g., with a scale in a closed container).
Compare mass and weight: give one similarity and one difference.
Similarity: both relate to the object. Difference: mass is intrinsic (doesn't change with location), weight depends on gravitational field (changes with location).
How does distance affect the gravitational force between two objects? Give a short explanation.
As distance increases, gravitational force decreases; specifically it decreases with the square of the distance.
What would happen to a planet's orbit if the mass of the Sun increased slightly? Explain whether the orbit would get larger, smaller, faster, or slower, and why.
If Sun mass increases, gravitational pull increases so planets would need higher orbital speed to remain in the same orbit; if speed doesn't change, orbits tend to become smaller (move closer) or orbiting period changes — generally stronger gravity pulls planets into tighter, faster orbits.
Describe how mass and the amount of matter are related.
Mass measures the amount of matter — if matter increases, mass increases; they are directly related.
If a student has a mass of 50 kg on Earth, what stays the same and what changes if they go to the Moon? (Explain briefly.)
Mass measures the amount of matter — if matter increases, mass increases; they are directly related.
How does the mass of each object affect the gravitational force between them? Provide a short explanation.
Greater masses increase gravitational force; larger masses attract each other more strongly.
What would happen to the planets’ orbits if the Sun lost a large portion of its mass suddenly? Explain the immediate effect.
If the Sun lost a large portion of its mass suddenly, its gravitational pull would weaken; planets could move into wider orbits or in extreme cases escape into space.
Explain how matter and gravity interact (use one clear example).
Gravity pulls matter toward other matter; e.g., an apple falls toward Earth because Earth’s mass creates a gravitational pull.
Explain why weight can change but mass cannot, using the idea of forces.
Because weight = gravitational force acting on an object, and that force depends on local gravity; mass is a property independent of external forces.
Write Newton's law of universal gravitation in equation form (show the variables and what they stand for).
Newton's law: F=Gm1m2r2F=Gr2m1m2 where FF is gravitational force, GG is the gravitational constant, m1m1 and m2m2 are the masses, and rr is the distance between their centers.
Explain how orbital speed depends on distance from the Sun and the Sun's mass (qualitatively — higher/lower and why).
Orbital speed is higher when a planet is closer to the Sun and when the Sun's mass is larger because stronger gravity requires greater sideways speed to balance the inward pull.