Topic: Force and Motion
Below is a list of key ideas related to Force and Motion. For each key idea, you will find a list of subideas, a list of items, results from our field testing, and a list of student misconceptions. After clicking on a tab, click on it again to close the tab.
A force is a push or a pull between two objects.
Students are expected to know that:
 A force is an interaction between objects, not a property of an object or something that resides within an object.
 Forces can be interactions between two objects in direct contact with each other or operating at a distance as in the case of gravity or a magnetic force.
 Forces between objects in direct contact with each other can be passive, such as a book setting on a table, or active, such as the pushes and pulls of mechanical devices or caused by various human activities.
Item ID Number 
Knowledge Being Assessed 
Grades 
Grades 
Select This Item for My Item Bank 

73% 
79% 

A ball does not acquire a force when it is rolled off a table. 
28% 
21% 

26% 
21% 
Misconception 
Student Misconception 
Grades 
Grades 

67% 
75% 

Passive objects (stationary rope, tabletop) cannot exert a force (AAAS Project 2061, n.d.). 
18% 
15% 
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.
The magnitude of two forces can be added together.
Students are expected to know that:
 Arrows can be used to represent forces acting on an object. The length of the arrows represents the strength of the forces, and the direction of the arrows represents the direction of the forces.
 Two forces acting on an object in the same direction at the same time are equivalent to a single force that is stronger than either of the two individual forces and is in the same direction as the two individual forces.
 Two forces acting on an object in opposite directions at the same time are equivalent to a single force that is weaker than the stronger of the two individual forces and is in the same direction as the stronger of the two individual forces.
 Two forces of the same strength acting on an object in opposite directions at the same time will cancel one another.
Boundaries:
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time, that act along the object’s line of motion.
 Students are expected to combine forces qualitatively, but they are not expected to calculate net force.
Misconception 
Student Misconception 
Grades 
Grades 

46% 
25% 

13% 
11% 

9% 
10% 
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.
If a force acts on an object in the same direction as the direction of its motion, the object’s speed will continue to increase while the force is acting.
Students are expected to know that:
 If a force is acting on an object to push or pull it forward, the object will continue to move faster and faster in the forward direction the entire time the force is acting.
 If an object’s speed is increasing, then a force must be acting on the object the entire time its speed is increasing.
Boundaries:
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time that act along the object’s line of motion. Students are not expected to analyze situations in which the force is acting at an angle other than along the object’s line of motion, which would change the direction of the object’s motion.
 Test items will involve situations in which forces are constant, not situations in which the forces are increasing or decreasing.
Misconception 
Student Misconception 
Grades 
Grades 

42% 
46% 

23% 
25% 

24% 
19% 

20% 
16% 

18% 
15% 
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.
If a force acts on an object in the direction opposite to the direction of the object’s motion, the object’s speed will continue to decrease while the force is acting.
Students are expected to know that:
 If a force, either constant or changing, acts on an object in the direction opposite to the direction of the object’s motion, the object’s speed will decrease and will continue to decrease for as long as that force is greater than any force moving the object forward.
 If an object’s speed is decreasing, a force must be acting on the object in the direction opposite to the direction of the object’s motion, and that opposing force must be greater than any force moving the object forward.
 If a force acts on an object in the direction opposite to the direction of the object’s motion for a long enough time, the object’s speed will decrease to zero. If the same force continues to act, the object will move in the direction opposite to its previous motion.
Boundaries:
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time, and each force must act along the object’s line of motion or, if the object is not moving, the forces are acting along the same line.
 Test items will involve situations in which forces are constant, not situations in which the forces are increasing or decreasing.
Misconception 
Student Misconception 
Grades 
Grades 

24% 
20% 

24% 
20% 

20% 
22% 

20% 
19% 

When the force on a moving object is constant, the object will slow down. 
21% 
15% 

18% 
17% 

20% 
11% 

18% 
14% 

9% 
7% 
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.
A moving object will maintain the same speed and direction of motion unless a force acts on it.
Students are expected to know that:
 If no forces (or forces that add to zero) act on a moving object, then the object will maintain a constant speed.
 If an object is maintaining a constant speed (or is at rest), then no forces (or forces that add to zero) are acting on it.
Boundaries
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time, and each force must act along the object’s line of motion.
 Items will not include situations in which objects are at rest.
Item ID Number 
Knowledge Being Assessed 
Grades 
Grades 
Select This Item for My Item Bank 

34% 
46% 

It is possible for an object to be moving at constant speed without a force pushing or pulling it. 
26% 
35% 
Misconception 
Student Misconception 
Grades 
Grades 

A constant force is needed to keep an object moving at constant speed. 
43% 
40% 

21% 
18% 

11% 
8% 

11% 
8% 
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.
If a force acts on an object in the same direction as the direction of its motion, the object’s speed will continue to increase while the force is acting.
and
If a force acts on an object in the direction opposite to the direction of the object’s motion, the object’s speed will continue to decrease while the force is acting.
These items have been aligned to more than one key idea. To view the subideas click on a key idea below.

If a force acts on an object in the same direction as the direction of its motion, the object’s speed will continue to increase while the force is acting.
Students are expected to know that:
 If a force is acting on an object to push or pull it forward, the object will continue to move faster and faster in the forward direction the entire time the force is acting.
 If an object’s speed is increasing, then a force must be acting on the object the entire time its speed is increasing.
Boundaries:
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time that act along the object’s line of motion. Students are not expected to analyze situations in which the force is acting at an angle other than along the object’s line of motion, which would change the direction of the object’s motion.
 Test items will involve situations in which forces are constant, not situations in which the forces are increasing or decreasing.

If a force acts on an object in the direction opposite to the direction of the object’s motion, the object’s speed will continue to decrease while the force is acting.
Students are expected to know that:
 If a force, either constant or changing, acts on an object in the direction opposite to the direction of the object’s motion, the object’s speed will decrease and will continue to decrease for as long as that force is greater than any force moving the object forward.
 If an object’s speed is decreasing, a force must be acting on the object in the direction opposite to the direction of the object’s motion, and that opposing force must be greater than any force moving the object forward.
 If a force acts on an object in the direction opposite to the direction of the object’s motion for a long enough time, the object’s speed will decrease to zero. If the same force continues to act, the object will move in the direction opposite to its previous motion.
Boundaries:
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time, and each force must act along the object’s line of motion or, if the object is not moving, the forces are acting along the same line.
 Test items will involve situations in which forces are constant, not situations in which the forces are increasing or decreasing.
Misconception 
Student Misconception 
Grades 
Grades 

20% 
16% 

19% 
15% 
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.
If a force acts on an object in the same direction as the direction of its motion, the object’s speed will continue to increase while the force is acting.
and
A moving object will maintain the same speed and direction of motion unless a force acts on it.
These items have been aligned to more than one key idea. To view the subideas click on a key idea below.

If a force acts on an object in the same direction as the direction of its motion, the object’s speed will continue to increase while the force is acting.
Students are expected to know that:
 If a force is acting on an object to push or pull it forward, the object will continue to move faster and faster in the forward direction the entire time the force is acting.
 If an object’s speed is increasing, then a force must be acting on the object the entire time its speed is increasing.
Boundaries:
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time that act along the object’s line of motion. Students are not expected to analyze situations in which the force is acting at an angle other than along the object’s line of motion, which would change the direction of the object’s motion.
 Test items will involve situations in which forces are constant, not situations in which the forces are increasing or decreasing.

A moving object will maintain the same speed and direction of motion unless a force acts on it.
Students are expected to know that:
 If no forces (or forces that add to zero) act on a moving object, then the object will maintain a constant speed.
 If an object is maintaining a constant speed (or is at rest), then no forces (or forces that add to zero) are acting on it.
Boundaries
 Students are expected to analyze situations involving no more than two forces acting on an object at the same time, and each force must act along the object’s line of motion.
 Items will not include situations in which objects are at rest.
Misconception 
Student Misconception 
Grades 
Grades 

A constant force is needed to keep an object moving at constant speed. 
47% 
51% 
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.