Key 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.
Item ID Number 
Knowledge Being Assessed  Grades 6–8 
Grades 9–12 
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24% 
21% 
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.