Evidence for Gravity - Middle School Physical Science
Card 1 of 25
What is the formula for gravitational force between two masses?
What is the formula for gravitational force between two masses?
Tap to reveal answer
$F_g = G\frac{m_1m_2}{r^2}$. Newton's law shows force depends on both masses and inversely on distance squared.
$F_g = G\frac{m_1m_2}{r^2}$. Newton's law shows force depends on both masses and inversely on distance squared.
← Didn't Know|Knew It →
Which variable in $F_g = G\frac{m_1m_2}{r^2}$ represents the distance between centers?
Which variable in $F_g = G\frac{m_1m_2}{r^2}$ represents the distance between centers?
Tap to reveal answer
$r$. Distance is measured between the centers of mass of the two objects.
$r$. Distance is measured between the centers of mass of the two objects.
← Didn't Know|Knew It →
What happens to gravitational force if distance $r$ is doubled in a simulation?
What happens to gravitational force if distance $r$ is doubled in a simulation?
Tap to reveal answer
Force becomes $\frac{1}{4}$ as large. Doubling distance makes $r^2$ become $4r^2$, reducing force by factor of 4.
Force becomes $\frac{1}{4}$ as large. Doubling distance makes $r^2$ become $4r^2$, reducing force by factor of 4.
← Didn't Know|Knew It →
What happens to gravitational force if distance $r$ is tripled in a simulation?
What happens to gravitational force if distance $r$ is tripled in a simulation?
Tap to reveal answer
Force becomes $\frac{1}{9}$ as large. Tripling distance makes $r^2$ become $9r^2$, reducing force by factor of 9.
Force becomes $\frac{1}{9}$ as large. Tripling distance makes $r^2$ become $9r^2$, reducing force by factor of 9.
← Didn't Know|Knew It →
What happens to gravitational force if one mass is doubled while $r$ stays constant?
What happens to gravitational force if one mass is doubled while $r$ stays constant?
Tap to reveal answer
Force doubles. Force is directly proportional to each mass, so doubling one mass doubles force.
Force doubles. Force is directly proportional to each mass, so doubling one mass doubles force.
← Didn't Know|Knew It →
What happens to gravitational force if both masses are doubled while $r$ stays constant?
What happens to gravitational force if both masses are doubled while $r$ stays constant?
Tap to reveal answer
Force becomes $4$ times as large. Doubling both masses multiplies force by $2 \times 2 = 4$.
Force becomes $4$ times as large. Doubling both masses multiplies force by $2 \times 2 = 4$.
← Didn't Know|Knew It →
Which relationship should a correct gravity model show between force and distance?
Which relationship should a correct gravity model show between force and distance?
Tap to reveal answer
Inverse-square: $F_g \propto \frac{1}{r^2}$. Force decreases with the square of distance, not linearly.
Inverse-square: $F_g \propto \frac{1}{r^2}$. Force decreases with the square of distance, not linearly.
← Didn't Know|Knew It →
Which relationship should a correct gravity model show between force and each mass?
Which relationship should a correct gravity model show between force and each mass?
Tap to reveal answer
Direct: $F_g \propto m_1$ and $F_g \propto m_2$. Force increases linearly with each mass independently.
Direct: $F_g \propto m_1$ and $F_g \propto m_2$. Force increases linearly with each mass independently.
← Didn't Know|Knew It →
Identify the best claim supported if a simulation shows higher force for larger $m_1$ at fixed $r$.
Identify the best claim supported if a simulation shows higher force for larger $m_1$ at fixed $r$.
Tap to reveal answer
Gravitational force increases as mass increases. Direct proportionality means larger mass produces larger force.
Gravitational force increases as mass increases. Direct proportionality means larger mass produces larger force.
← Didn't Know|Knew It →
Identify the best claim supported if a simulation shows force decreases rapidly as $r$ increases.
Identify the best claim supported if a simulation shows force decreases rapidly as $r$ increases.
Tap to reveal answer
Gravitational force decreases with distance by an inverse-square pattern. Rapid decrease with distance indicates inverse-square relationship.
Gravitational force decreases with distance by an inverse-square pattern. Rapid decrease with distance indicates inverse-square relationship.
← Didn't Know|Knew It →
What is the direction of the gravitational force on each mass in a two-body model?
What is the direction of the gravitational force on each mass in a two-body model?
Tap to reveal answer
Along the line joining centers, toward the other mass. Gravity always pulls objects directly toward each other.
Along the line joining centers, toward the other mass. Gravity always pulls objects directly toward each other.
← Didn't Know|Knew It →
Which option states Newton's third law for gravitational interaction between two masses?
Which option states Newton's third law for gravitational interaction between two masses?
Tap to reveal answer
Forces are equal in magnitude and opposite in direction. Action-reaction pairs have equal magnitude but opposite directions.
Forces are equal in magnitude and opposite in direction. Action-reaction pairs have equal magnitude but opposite directions.
← Didn't Know|Knew It →
A model shows Earth pulls on the Moon with force $F$. What force does the Moon exert on Earth?
A model shows Earth pulls on the Moon with force $F$. What force does the Moon exert on Earth?
Tap to reveal answer
Also $F$, in the opposite direction. Newton's third law: forces between objects are equal and opposite.
Also $F$, in the opposite direction. Newton's third law: forces between objects are equal and opposite.
← Didn't Know|Knew It →
What is the formula for gravitational field strength due to a mass $M$ at distance $r$?
What is the formula for gravitational field strength due to a mass $M$ at distance $r$?
Tap to reveal answer
$g = G\frac{M}{r^2}$. Field strength at a point depends on source mass and distance from it.
$g = G\frac{M}{r^2}$. Field strength at a point depends on source mass and distance from it.
← Didn't Know|Knew It →
Find the missing evidence: If a graph of $F_g$ vs. $r$ is consistent with $\frac{1}{r^2}$, what claim is supported?
Find the missing evidence: If a graph of $F_g$ vs. $r$ is consistent with $\frac{1}{r^2}$, what claim is supported?
Tap to reveal answer
Gravitational force follows an inverse-square law with distance. Graph matching $\frac{1}{r^2}$ pattern confirms the inverse-square law.
Gravitational force follows an inverse-square law with distance. Graph matching $\frac{1}{r^2}$ pattern confirms the inverse-square law.
← Didn't Know|Knew It →
Identify the independent variable when a simulation changes only distance to test its effect on $F_g$.
Identify the independent variable when a simulation changes only distance to test its effect on $F_g$.
Tap to reveal answer
Distance $r$. Independent variable is what you change; dependent is what you measure.
Distance $r$. Independent variable is what you change; dependent is what you measure.
← Didn't Know|Knew It →
What happens to gravitational field strength $g$ if distance from the planet center is doubled?
What happens to gravitational field strength $g$ if distance from the planet center is doubled?
Tap to reveal answer
$g$ becomes $\frac{1}{4}$ as large. Field strength follows same inverse-square law as gravitational force.
$g$ becomes $\frac{1}{4}$ as large. Field strength follows same inverse-square law as gravitational force.
← Didn't Know|Knew It →
Which evidence from a simulation best supports that gravity is always attractive?
Which evidence from a simulation best supports that gravity is always attractive?
Tap to reveal answer
Objects always accelerate toward each other, never away. Attractive force means objects move toward each other, never repel.
Objects always accelerate toward each other, never away. Attractive force means objects move toward each other, never repel.
← Didn't Know|Knew It →
Which change best supports the claim that gravity decreases with distance in a simulation?
Which change best supports the claim that gravity decreases with distance in a simulation?
Tap to reveal answer
Increase $r$ while keeping $m_1$ and $m_2$ constant. Since $F \propto \frac{1}{r^2}$, increasing distance while fixing masses shows force decreases.
Increase $r$ while keeping $m_1$ and $m_2$ constant. Since $F \propto \frac{1}{r^2}$, increasing distance while fixing masses shows force decreases.
← Didn't Know|Knew It →
Which graph shape best matches the model prediction for $F$ versus $r$ when masses are constant?
Which graph shape best matches the model prediction for $F$ versus $r$ when masses are constant?
Tap to reveal answer
A decreasing curve proportional to $\frac{1}{r^2}$. The inverse square relationship creates a hyperbolic curve that decreases rapidly.
A decreasing curve proportional to $\frac{1}{r^2}$. The inverse square relationship creates a hyperbolic curve that decreases rapidly.
← Didn't Know|Knew It →
In a simulation, which variable must be controlled to isolate the effect of distance on $F$?
In a simulation, which variable must be controlled to isolate the effect of distance on $F$?
Tap to reveal answer
Keep $m_1$ and $m_2$ constant. Controlling masses isolates distance effects since $F$ depends on both variables.
Keep $m_1$ and $m_2$ constant. Controlling masses isolates distance effects since $F$ depends on both variables.
← Didn't Know|Knew It →
In a simulation, which variable must be controlled to isolate the effect of mass on $F$?
In a simulation, which variable must be controlled to isolate the effect of mass on $F$?
Tap to reveal answer
Keep $r$ constant. Controlling distance isolates mass effects since $F$ depends on both variables.
Keep $r$ constant. Controlling distance isolates mass effects since $F$ depends on both variables.
← Didn't Know|Knew It →
Which model result supports the claim that gravity is always attractive, not repulsive?
Which model result supports the claim that gravity is always attractive, not repulsive?
Tap to reveal answer
Objects accelerate toward each other, not away, for all tested masses. Attractive force means objects always pull together, never push apart.
Objects accelerate toward each other, not away, for all tested masses. Attractive force means objects always pull together, never push apart.
← Didn't Know|Knew It →
Which evidence from an orbit simulation best supports that gravity provides centripetal force?
Which evidence from an orbit simulation best supports that gravity provides centripetal force?
Tap to reveal answer
The orbiting object continuously accelerates toward the central mass. Gravity pulls the orbiting object inward, providing the centripetal acceleration for circular motion.
The orbiting object continuously accelerates toward the central mass. Gravity pulls the orbiting object inward, providing the centripetal acceleration for circular motion.
← Didn't Know|Knew It →
If a model uses $g = 10\ \text{N/kg}$ and $m = 3\ \text{kg}$, what is $F_g$?
If a model uses $g = 10\ \text{N/kg}$ and $m = 3\ \text{kg}$, what is $F_g$?
Tap to reveal answer
$30\ \text{N}$. Using $F_g = mg$: $F_g = 3\ \text{kg} \times 10\ \text{N/kg} = 30\ \text{N}$.
$30\ \text{N}$. Using $F_g = mg$: $F_g = 3\ \text{kg} \times 10\ \text{N/kg} = 30\ \text{N}$.
← Didn't Know|Knew It →