Motion Caused by Gravity - Middle School Physical Science
Card 1 of 25
What is gravity?
What is gravity?
Tap to reveal answer
An attractive force between masses. Gravity pulls all objects with mass toward each other.
An attractive force between masses. Gravity pulls all objects with mass toward each other.
← Didn't Know|Knew It →
What is the direction of the gravitational force on an object near Earth?
What is the direction of the gravitational force on an object near Earth?
Tap to reveal answer
Toward Earth’s center. Gravity always pulls objects toward the center of mass.
Toward Earth’s center. Gravity always pulls objects toward the center of mass.
← Didn't Know|Knew It →
What happens to $F_g$ if the distance between two objects is cut in half?
What happens to $F_g$ if the distance between two objects is cut in half?
Tap to reveal answer
It becomes $4$ times the original. Halving distance means $(\frac{1}{2})^2$ in denominator, so force quadruples.
It becomes $4$ times the original. Halving distance means $(\frac{1}{2})^2$ in denominator, so force quadruples.
← Didn't Know|Knew It →
What is the relationship between mass and gravitational force when distance is constant?
What is the relationship between mass and gravitational force when distance is constant?
Tap to reveal answer
Force is directly proportional to mass. From $F_g = G\frac{m_1m_2}{r^2}$, force increases linearly with either mass.
Force is directly proportional to mass. From $F_g = G\frac{m_1m_2}{r^2}$, force increases linearly with either mass.
← Didn't Know|Knew It →
What is the formula for weight near Earth’s surface?
What is the formula for weight near Earth’s surface?
Tap to reveal answer
$W = mg$. Weight is gravitational force on an object, where $g$ is Earth's surface gravity.
$W = mg$. Weight is gravitational force on an object, where $g$ is Earth's surface gravity.
← Didn't Know|Knew It →
Which quantity stays the same on the Moon: mass or weight?
Which quantity stays the same on the Moon: mass or weight?
Tap to reveal answer
Mass stays the same. Mass is intrinsic property; weight depends on local gravity.
Mass stays the same. Mass is intrinsic property; weight depends on local gravity.
← Didn't Know|Knew It →
What causes a thrown ball to curve downward after it leaves the hand?
What causes a thrown ball to curve downward after it leaves the hand?
Tap to reveal answer
Earth’s gravitational force accelerates it downward. Gravity acts continuously on projectiles, creating parabolic paths.
Earth’s gravitational force accelerates it downward. Gravity acts continuously on projectiles, creating parabolic paths.
← Didn't Know|Knew It →
What is the acceleration of an object in free fall near Earth (ignoring air resistance)?
What is the acceleration of an object in free fall near Earth (ignoring air resistance)?
Tap to reveal answer
$g \approx 9.8\ \text{m/s}^2$ downward. All objects fall with same acceleration regardless of mass.
$g \approx 9.8\ \text{m/s}^2$ downward. All objects fall with same acceleration regardless of mass.
← Didn't Know|Knew It →
Which falls faster in a vacuum: a $1\ \text{kg}$ rock or a $10\ \text{kg}$ rock?
Which falls faster in a vacuum: a $1\ \text{kg}$ rock or a $10\ \text{kg}$ rock?
Tap to reveal answer
They fall at the same rate. In vacuum, all objects accelerate at $g$ regardless of mass.
They fall at the same rate. In vacuum, all objects accelerate at $g$ regardless of mass.
← Didn't Know|Knew It →
What provides the centripetal force that keeps the Moon in orbit around Earth?
What provides the centripetal force that keeps the Moon in orbit around Earth?
Tap to reveal answer
Earth’s gravitational force. Gravity provides the inward force needed for circular motion.
Earth’s gravitational force. Gravity provides the inward force needed for circular motion.
← Didn't Know|Knew It →
Which has stronger gravitational pull on you: Earth or the Moon?
Which has stronger gravitational pull on you: Earth or the Moon?
Tap to reveal answer
Earth. Earth's mass and proximity create much stronger gravitational field.
Earth. Earth's mass and proximity create much stronger gravitational field.
← Didn't Know|Knew It →
Which location has the greatest gravitational force from Earth: $r$, $2r$, or $3r$ from Earth’s center?
Which location has the greatest gravitational force from Earth: $r$, $2r$, or $3r$ from Earth’s center?
Tap to reveal answer
At $r$. Gravitational force decreases with distance squared from center.
At $r$. Gravitational force decreases with distance squared from center.
← Didn't Know|Knew It →
What happens to an object’s weight if $g$ decreases while its mass stays constant?
What happens to an object’s weight if $g$ decreases while its mass stays constant?
Tap to reveal answer
Weight decreases. Since $W = mg$, weight is proportional to gravitational acceleration.
Weight decreases. Since $W = mg$, weight is proportional to gravitational acceleration.
← Didn't Know|Knew It →
What is the action–reaction pair when Earth pulls on an object with gravity?
What is the action–reaction pair when Earth pulls on an object with gravity?
Tap to reveal answer
The object pulls on Earth with equal gravitational force. Newton's third law: forces always come in equal and opposite pairs.
The object pulls on Earth with equal gravitational force. Newton's third law: forces always come in equal and opposite pairs.
← Didn't Know|Knew It →
What happens to gravitational force when the mass of one or both objects increases?
What happens to gravitational force when the mass of one or both objects increases?
Tap to reveal answer
It increases as mass increases. Force is directly proportional to the product of masses.
It increases as mass increases. Force is directly proportional to the product of masses.
← Didn't Know|Knew It →
State the inverse-square relationship for gravity with distance $r$.
State the inverse-square relationship for gravity with distance $r$.
Tap to reveal answer
Gravitational force is proportional to $ rac{1}{r^2}$. This means force decreases by factor of 4 when distance doubles.
Gravitational force is proportional to $ rac{1}{r^2}$. This means force decreases by factor of 4 when distance doubles.
← Didn't Know|Knew It →
What is weight, in terms of gravity and mass?
What is weight, in terms of gravity and mass?
Tap to reveal answer
Weight is the gravitational force on a mass. Measured in newtons (N), not kilograms.
Weight is the gravitational force on a mass. Measured in newtons (N), not kilograms.
← Didn't Know|Knew It →
State the formula that relates weight $W$, mass $m$, and gravitational field strength $g$.
State the formula that relates weight $W$, mass $m$, and gravitational field strength $g$.
Tap to reveal answer
$W = mg$. Where $g$ is gravitational field strength in m/s².
$W = mg$. Where $g$ is gravitational field strength in m/s².
← Didn't Know|Knew It →
If one object's mass doubles while distance stays the same, what happens to gravitational force?
If one object's mass doubles while distance stays the same, what happens to gravitational force?
Tap to reveal answer
It doubles. Force is directly proportional to each mass.
It doubles. Force is directly proportional to each mass.
← Didn't Know|Knew It →
If distance triples from $r$ to $3r$, what fraction of the original gravitational force remains?
If distance triples from $r$ to $3r$, what fraction of the original gravitational force remains?
Tap to reveal answer
It becomes $ rac{1}{9}$ of the original force. Since force ∝ $ rac{1}{r^2}$, tripling $r$ gives $ rac{1}{(3r)^2} = rac{1}{9r^2}$.
It becomes $ rac{1}{9}$ of the original force. Since force ∝ $ rac{1}{r^2}$, tripling $r$ gives $ rac{1}{(3r)^2} = rac{1}{9r^2}$.
← Didn't Know|Knew It →
Choose the correct comparison: On the Moon, an astronaut's mass is $__$ and weight is $__$.
Choose the correct comparison: On the Moon, an astronaut's mass is $__$ and weight is $__$.
Tap to reveal answer
Mass is the same; weight is smaller. Mass is intrinsic; weight depends on local gravity (Moon's is ~1/6 Earth's).
Mass is the same; weight is smaller. Mass is intrinsic; weight depends on local gravity (Moon's is ~1/6 Earth's).
← Didn't Know|Knew It →
What is the acceleration of an object in free fall near Earth (ignore air resistance)?
What is the acceleration of an object in free fall near Earth (ignore air resistance)?
Tap to reveal answer
Approximately $9.8\ \text{m/s}^2$ downward. This value is constant for all objects regardless of mass.
Approximately $9.8\ \text{m/s}^2$ downward. This value is constant for all objects regardless of mass.
← Didn't Know|Knew It →
Identify the key difference between mass and weight.
Identify the key difference between mass and weight.
Tap to reveal answer
Mass is amount of matter; weight is gravitational force. Mass stays constant everywhere; weight varies with gravity.
Mass is amount of matter; weight is gravitational force. Mass stays constant everywhere; weight varies with gravity.
← Didn't Know|Knew It →
Which option best explains why planets orbit the Sun instead of moving in a straight line?
Which option best explains why planets orbit the Sun instead of moving in a straight line?
Tap to reveal answer
Gravity provides centripetal acceleration toward the Sun. This inward force curves their path into elliptical orbits.
Gravity provides centripetal acceleration toward the Sun. This inward force curves their path into elliptical orbits.
← Didn't Know|Knew It →
What is the cause of tides on Earth in terms of gravitational interactions?
What is the cause of tides on Earth in terms of gravitational interactions?
Tap to reveal answer
Uneven gravitational pull from the Moon (and the Sun). Water bulges toward and away from the Moon due to differential forces.
Uneven gravitational pull from the Moon (and the Sun). Water bulges toward and away from the Moon due to differential forces.
← Didn't Know|Knew It →