Key Idea: The gravitational potential energy of an object near the surface of the earth is related to the distance the object is above the surface of the earth (or an alternate reference point), and the mass of the object.

Students should know that:

  1. Objects that are zero distance from the reference point (i.e. the surface of the earth) have no gravitational potential energy.
  2. The gravitational potential energy of an object is related to both the distance the object is above the surface of the earth and the mass of the object, and the amount of gravitational potential energy an object has can be determined from these two factors alone.
  3. When an object is lifted above the surface of the earth, the change in its gravitational potential energy is related to the change in the height, not to the path taken to get there. Another way of saying this is that the amount of gravitational potential energy an object has is independent of its history (e.g. the path the object takes to get to the height above the reference point). 
  4. For objects that have the same mass, the object farthest from the surface of the earth will have the most gravitational potential energy and the object closest to the surface of the earth will have the least gravitational potential energy.
  5. For objects that are equal distances from the surface of the earth (greater than zero), the object with the greatest mass will have the most gravitational potential energy, and the object with the least mass will have the least gravitational potential energy.

 

Boundaries:

  1. The distance used in the assessment items is the distance above the surface of the earth unless a substitute reference plane, such as the floor, is explicitly stated in the assessment item.  When this is the case, the reference plane is chosen so that there will be only positive values for the distance.
  2. Assessment items are limited to systems involving the earth.
  3. Students are not expected to know the difference between “weight” and “mass.”  All of the contexts used in the assessment items are ones where “mass” and “weight” are proportional to each other.  The earth is used as the context for all assessment items aligned to this idea.
  4. Assessment items use the phrase “gravitational potential energy” and not “gravitational energy” because students often confuse “gravitational energy” with “gravitational force.”
  5. Assessment items expect students to compare relative distances and masses to determine relative amounts of gravitational potential energy. Students are not expected to calculate the exact amount of gravitational potential energy.

 

NOTE: Any plane on which all points are essentially equidistant from the center of the earth, such as the floor of a room, can be used as a substitute for the center of the earth in determining the amount of gravitational potential energy an object has. Because all points on this reference plane are considered to be equidistant from the center of the earth, all objects on the plane can be considered to have zero gravitational potential energy. (There will be only one reference plane that applies to all objects in the situation.) In assessment items the “reference plane” will be referred to as a “reference point.”

Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
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EG017004

For two students of equal height and weight, the student standing on the higher diving board has more gravitational potential energy than the student standing on the lower diving board.

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EG088002

When two children who weigh the same are on a teeter-totter, the child who is up has more gravitational potential energy than the child who is down.

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EG089001

Two apples hanging from a tree will have different amounts of gravitational potential energy if one is hanging higher in the tree than the other.

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EG091001

Two airplanes that are flying at same distance from the ground will have the same amount of gravitational potential energy if they have the same mass.

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EG019005

When a bird is flying with a stick in its mouth, the bird has more gravitational potential energy because it weighs more than the stick.

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EG087001

A coconut has the most gravitational potential energy before it falls from a tree because a coconut is at the highest point above the ground before it falls.

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EG067002

The gravitational potential energy of a space shuttle increases as it gets higher in the sky.

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EG022004

A person will have the same amount of gravitational potential energy at the top of a mountain regardless of the path the person takes to get there.

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RG178001

When a bird and a piece of food are at the same height above the ground, the bird has more gravitational potential energy because the it has more mass than the food.

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RG169002

Three people have the same amount of gravitational potential energy when they are all on the same floor of a building because gravitational potential energy depends on how high the object’s final position is above the earth.

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EG090002

Two identical balls that are thrown up in the air will have the same amount of gravitational potential energy when they are at the same height above the ground.

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EG014003

The gravitational potential energy of an object decreases as it falls.

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RG179001

The gravitational potential energy of a falling rock at 50 meters is half of the gravitational potential energy at 100 meters because the amount of gravitational potential energy an object has is directly proportional to the height the object is above the ground.

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RG134002

An elevator carrying more mass will have more gravitational potential energy than an identical elevator carrying less mass because gravitational potential energy increases as mass increases.

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EG069002

For two boxes that have the same amount of gravitational potential energy, the box that is on the lower shelf weighs more.

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Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

EGM061

The gravitational potential energy of an object does not depend on the distance the object is above the ground (AAAS Project 2061, n.d.).

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EGM060

For two identical objects thrown up into the air, they must have been thrown with the same amount of force to have the same amount of gravitational potential energy (AAAS Project 2061, n.d.).

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EGM053

The gravitational potential energy of an object decreases as an object moves farther away from the center of the earth and the gravitational potential energy increases as the object falls toward the earth (AAAS Project 2061, n.d.).

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EGM048

Living things give inanimate objects energy by carrying or pushing them. For example, a person gives a bike energy by riding it or a bird give a stick energy by carrying it (Herrmann-Abell & DeBoer, 2010).

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EGM047

The gravitational potential energy of an object depends on the direction the object is traveling. For example, some students think that an object traveling upward has more gravitational potential energy than an object traveling downward even if they are the same mass and are at the same distance above the ground (Loverude, 2004).

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EGM044

Gravitational potential energy is the potential to fall; an object will lose all of its gravitational potential energy as soon as it starts to fall (Herrmann-Abell & DeBoer, 2010; Loverude, 2004).

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EGM043

The gravitational potential energy of an object depends only on the mass/weight of the object, not its height above the ground (AAAS Project 2061, n.d.).

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EGM042

The gravitational potential energy of an object depends on the speed of the object (the gravitational potential energy increases as the object's speed increases) (Herrmann-Abell & DeBoer, 2010).

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EGM040

The gravitational potential energy of an object depends upon the path the object takes to get to the distance above the reference point (Singh & Rosengrant, 2001, 2003; Herrmann-Abell & DeBoer, 2010).

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EGM038

The gravitational potential energy of an object does not depend on the mass of the object (AAAS Project 2061, n.d.).

See the Original Project

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.

NGSS Statements

Code

Statement

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.

PS3.A MS

A system of objects may also contain stored (potential) energy, depending on their relative positions.