## 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.

Students are expected to know that:

1. 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.
2. If an object’s speed is increasing, then a force must be acting on the object the entire time its speed is increasing.

Boundaries:

1. 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.
2. Test items will involve situations in which forces are constant, not situations in which the forces are increasing or decreasing.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
6–8
9–12
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Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

6–8
9–12

FMM129

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

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FMM125

When a force acts on a moving object to slow the object down, the object will slow down for a while and then move at a lower constant speed (AAAS Project 2061, n.d.).

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FMM124

When a force acts on a moving object in the direction opposite the object’s direction of motion, the object will move at a constant speed for a while and then slow down (AAAS Project 2061, n.d.).

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FMM120

When a force acts on an object in the direction of the object’s motion, the speed of the object will stay the same for a while and then increase and stay at the new higher speed. (AAAS Project 2061, n.d.)

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FMM118

When a force acts on an object in the direction of the object’s motion, the speed of the object will increase for a while and then slow down. (AAAS Project 2061, n.d.)

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FMM117

When a force acts on an object in the direction of the object's motion, the speed of the object will increase for a while and then level off at the higher speed (AAAS Project 2061, n.d.).

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FMM102

Constant force produces constant speed. Under the influence of a constant force, objects move with constant velocity (Champagne et al., 1980).

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FMM101

Increasing speed requires increasing force.

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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

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.

PS2.A MS

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

PS2.A HS

Newton's second law accurately predicts changes in the motion of macroscopic objects.