AP Physics 1: Algebra-Based Practice Quiz: Systems and Center of Mass
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Test your understanding with short quizzes. This quiz has 16 questions to check your progress.
Question 1 of 16
All Questions (16)
A) The system's overall velocity
B) The external forces acting on the system
C) The interactions between objects within the system
D) The shape of the system's container
Correct Answer: C
Content point 3 states: 'System properties are determined by the interactions between objects within the system.' This means the internal workings, not external factors, define the system's inherent properties.
A) At its north pole
B) On its surface at the equator
C) At its geometric center
D) The location is constantly changing as it rotates
Correct Answer: C
Content point 5 states: 'For systems with symmetrical mass distributions, the center of mass is located on lines of symmetry.' For a sphere, the geometric center is the intersection of all lines of symmetry.
A) When analyzing the vibration of the engine's pistons
B) When calculating the car's overall trajectory on a highway
C) When determining the stress on an individual tire
D) When studying the combustion process in a cylinder
Correct Answer: B
Content point 4 explains that a system can be treated as a single object if the properties or interactions of its constituent parts are not important for the model. For calculating the car's overall trajectory, the internal workings (pistons, tires) are not important, and the car can be modeled as a single object.
A) Exactly halfway between the two objects
B) Closer to the 2 kg object
C) Closer to the 10 kg object
D) At the exact location of the 10 kg object
Correct Answer: C
Content point 2 states that the center of mass's location is described with respect to its constituent parts. The center of mass is a weighted average of the positions of the mass. Therefore, it will always be located closer to the object with the greater mass.
A) a complex path that combines rotation and linear motion.
B) a simple parabolic path, as if it were a single particle.
C) a straight line, regardless of gravity.
D) stationary, while the rest of the hammer moves around it.
Correct Answer: B
Content point 7 states: 'A system can be modeled as a singular object that is located at the system's center of mass.' When a complex object like a hammer is thrown, its center of mass follows the simple trajectory of a projectile (a parabola) under gravity, ignoring air resistance.
A) The location of the heaviest part of the system.
B) The geometric center of the system's volume.
C) A single point where the system's total mass can be considered to be concentrated for modeling its motion.
D) The only point in a system that cannot be moved.
Correct Answer: C
This is the core concept from content point 7, which states that a system can be modeled as a singular object located at the system's center of mass. This implies that for translational motion, the mass acts as if it's all at that one point.
A) It is in the same location as the original square's center of mass.
B) It is located at the corner with the 90-degree angle.
C) It is located on the triangle's line of symmetry.
D) It is located outside the physical material of the triangle.
Correct Answer: C
The new triangular piece, while not as symmetric as the original square, still has one line of symmetry running from the 90-degree corner to the midpoint of the opposite side. According to content point 5, the center of mass must be located on this line.
A) The gravitational force exerted by the Milky Way galaxy on the Sun.
B) The gravitational force exerted by Jupiter on Saturn.
C) The light from a distant star reaching Jupiter.
D) A comet from outside the solar system passing by Saturn.
Correct Answer: B
Content points 1 and 3 describe systems in terms of the properties and interactions of their constituent parts. Since the system is defined as the Sun, Jupiter, and Saturn, the gravitational pull between Jupiter and Saturn is an interaction between objects within the system.
A) It moves from x = 2 m to x = 3 m.
B) It moves from x = 2 m to x = 4 m.
C) It moves from x = 3 m to x = 4 m.
D) It does not change because the masses are equal.
Correct Answer: A
According to content point 6, the location of the center of mass can be calculated. Initially, with equal masses, it is at the midpoint: x = 2 m. After moving one mass, the new location is the average of the positions: (0 m + 6 m) / 2 = 3 m. Therefore, it moves from x = 2 m to x = 3 m.
A) Calculating the total momentum of a galaxy moving through space.
B) Predicting the landing spot of a thrown, non-spinning ball.
C) Describing how a figure skater's spin rate changes as she pulls in her arms.
D) Determining the orbit of a binary star system around a galactic core.
Correct Answer: C
Content point 4 notes that the single-object model is inappropriate when internal interactions are important. For a figure skater, the change in spin rate is caused by the redistribution of mass (pulling arms in), which is an interaction of the constituent parts of the system (her body). This internal change is the key feature, so the single-object model is not useful.
A) the heaviest part of the system.
B) a point outside the system.
C) the geometric origin (0,0).
D) a line of symmetry.
Correct Answer: D
This is a direct application of content point 5: 'For systems with symmetrical mass distributions, the center of mass is located on lines of symmetry.'
A) Evenly distributed along the material of the ring.
B) On the outer edge of the ring.
C) At the geometric center of the ring, in the empty space.
D) On the inner edge of the ring.
Correct Answer: C
The ring has a symmetrical mass distribution. According to content point 5, the center of mass is located on its lines of symmetry. The intersection of all diameters (lines of symmetry) is the geometric center. This demonstrates that the center of mass can be located at a point where there is no physical matter.
A) Slightly above the center of the plank.
B) At the exact center of the plank.
C) Slightly below the center of the plank.
D) At one end of the plank.
Correct Answer: B
The center of mass of the uniform plank is at its center. The steel block is also placed at the center. Since both constituent parts of the system have their mass centered at the same point, the center of mass for the combined system remains at that same central point, based on the principles of calculating its location from its parts (content points 2 and 6).
A) is determined only by external forces, simplifying calculations.
B) perfectly describes the rotational motion of the system's parts.
C) is always zero.
D) is determined only by the internal forces between the system's parts.
Correct Answer: A
Content point 7 states a system can be modeled as a singular object at its center of mass. The motion of this point (the center of mass) is governed by Newton's second law considering only the net external force on the system. This simplifies analysis by allowing us to ignore the complex internal forces and torques that cause rotation.
A) The system is always simpler than its parts.
B) The properties of the system are determined by the interactions of its parts.
C) The parts of a system must all have equal mass.
D) A system cannot be broken down into smaller parts.
Correct Answer: B
This is a direct restatement of the concept in content point 3: 'System properties are determined by the interactions between objects within the system.' It also aligns with content point 1, which involves describing the properties and interactions of a system.
A) At the exact corner where the two bars join.
B) At the midpoint of the vertical bar.
C) In the empty space 'inside' the corner of the L-shape.
D) At the midpoint of the horizontal bar.
Correct Answer: C
The center of mass of the vertical bar is at its own center, and the center of mass of the horizontal bar is at its own center. The center of mass of the combined system must lie on a line connecting these two points. By symmetry (if you imagine a 45-degree line from the corner), the center of mass will be pulled inward from that connecting line, placing it in the empty space inside the L. This combines the concepts of symmetry (point 5) and calculating location based on constituent parts (points 2 and 6).