AP Physics 1: Algebra-Based Flashcards: Newton's Third Law
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 11 cards to help you master important concepts.
What causes the internal forces that result in tension within a string or cable?
The forces that create tension are a response to an external force being applied to the string or system.
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What causes the internal forces that result in tension within a string or cable?
The forces that create tension are a response to an external force being applied to the string or system.
If two objects within a system push off each other, why doesn't the system's center of mass motion change?
The motion of the system's center of mass is not influenced because the forces the objects exert on each other are internal to the system.
What is Newton's third law?
Newton's third law describes the interaction of two objects in terms of the paired forces that each exerts on the other.
Define tension.
Tension is the macroscopic net result of forces that segments of a string, cable, or similar system exert on each other in response to an external force.
How would you represent the forces between two interacting objects based on Newton's third law?
The forces would be represented as a pair, with one force exerted on the first object and the other force exerted on the second object.
How do Newton's third law force pairs relate to internal forces in a system?
The paired forces described by Newton's third law are considered internal forces when the two interacting objects are defined as being part of the same system.
What are internal forces in the context of a system?
Internal forces are the forces from interactions between objects that are within the same system.
How are the forces between two interacting objects described by Newton's third law?
The two objects exert paired forces on each other.
What is the effect of internal forces on the motion of a system's center of mass?
Interactions between objects within a system (internal forces) do not influence the motion of that system's center of mass.
What is a key property of tension in an ideal string?
The tension in an ideal string is the same at all points within the string.
An ideal string is pulled from both ends. If the tension at one end is T, what is the tension at the center of the string?
The tension is the same at all points within an ideal string, so the tension at the center is also T.