AP Physics 1 Flashcards: Reference Frames And Relative Motion

What this deck covers

This deck focuses on Reference Frames And Relative Motion, giving you a quick way to review the definitions, rules, and examples that matter most for AP Physics 1.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What happens to observed motion if the observer's frame accelerates?

Answer: Observed motion appears non-uniform. Acceleration creates fictitious forces in the observer's frame.

Flashcard 2: Identify the reference frame: A car moving at 60 km/h north.

Answer: Reference frame: Earth's surface. The ground is the stationary reference from which speed is measured.

Flashcard 3: How does velocity change between two reference frames?

Answer: Velocity changes by the vector difference between the frames. Vector subtraction gives the relative velocity between frames.

Flashcard 4: What is meant by 'rest frame'?

Answer: The reference frame in which an object is at rest. The frame where the object has zero velocity.

Flashcard 5: Identify the correct relative speed: Two trains, 60 m/s and 40 m/s opposite directions.

Answer: Relative speed = 100 m/s. Add speeds for opposite directions: $60 + 40 = 100$ m/s.

Flashcard 6: What is the observer's frame if they see a moving object stationary?

Answer: The observer's frame moves with the object. Observer and object share the same velocity.

Flashcard 7: What is meant by 'rest frame'?

Answer: The reference frame in which an object is at rest. The frame where the object has zero velocity.

Flashcard 8: What does it mean when two objects have zero relative velocity?

Answer: They move together at the same speed and direction. No relative motion means identical velocity vectors.

Flashcard 9: What does an observer in a non-inertial frame perceive?

Answer: Perceived forces not due to physical interactions. Acceleration creates apparent forces not from real interactions.

Flashcard 10: Identify the correct velocity: Train moving at 30 m/s east, observed from a car moving 10 m/s east.

Answer: Relative velocity = 20 m/s east. Subtract car velocity from train velocity: $30 - 10 = 20$ m/s.

Flashcard 11: Identify the inertial frame: A stationary train platform.

Answer: The platform is an inertial frame. No acceleration means it's an inertial reference frame.

Flashcard 12: What happens to observed motion if the observer's frame accelerates?

Answer: Observed motion appears non-uniform. Acceleration creates fictitious forces in the observer's frame.

Flashcard 13: What is the main difference between inertial and non-inertial frames?

Answer: Inertial frames have no acceleration; non-inertial frames do. Acceleration distinguishes non-inertial from inertial frames.

Flashcard 14: Determine the relative velocity: Object A = 25 m/s, Object B = 15 m/s opposite.

Answer: Relative velocity = 40 m/s. Add speeds for opposite directions: $25 + 15 = 40$ m/s.

Flashcard 15: Find the velocity of a car relative to a cyclist: Car = 20 m/s, Cyclist = 5 m/s.

Answer: Relative velocity = 15 m/s. Subtract velocities in same direction: $20 - 5 = 15$ m/s.

Flashcard 16: What is the relative velocity when two objects move in opposite directions?

Answer: The sum of their speeds. Add speeds when objects approach each other.

Flashcard 17: Explain how to determine relative motion using vectors.

Answer: Use vector addition or subtraction. Vector operations account for direction in relative motion.

Flashcard 18: Find the velocity of a boat: River speed = 5 m/s, Boat speed = 8 m/s downstream.

Answer: Velocity = 13 m/s downstream. Add velocities when moving in the same direction: $8 + 5 = 13$ m/s.

Flashcard 19: What is a Galilean transformation?

Answer: Transformation relating measurements in inertial frames. It converts coordinates between frames moving at constant velocity.

Flashcard 20: Which frame is at rest when observing two moving cars?

Answer: The frame in which the observer is stationary. The observer defines their own frame as the rest frame.

Flashcard 21: What is the formula for relative velocity between two objects?

Answer: $v_{AB} = v_A - v_B$. Subtract object B's velocity from object A's velocity.

Flashcard 22: State the principle of relative motion.

Answer: Motion is relative to the observer's reference frame. All motion measurements depend on the chosen reference frame.

Flashcard 23: What is a reference frame in physics?

Answer: A reference frame is a perspective from which motion is observed. It's the coordinate system from which we measure positions and motions.

Flashcard 24: What is the main difference between inertial and non-inertial frames?

Answer: Inertial frames have no acceleration; non-inertial frames do. Acceleration distinguishes non-inertial from inertial frames.

Flashcard 25: State the effect of changing reference frames on velocity.

Answer: Velocity is relative and changes with the frame. Changing frames changes the measured velocity value.

Flashcard 26: What does an object's path look like in a rotating reference frame?

Answer: It appears curved due to fictitious forces. Rotation creates apparent forces like centrifugal force.

Flashcard 27: Which frame experiences fictitious forces?

Answer: Non-inertial frames. Acceleration creates fictitious forces in these frames.

Flashcard 28: Choose the correct statement about observers in relative motion.

Answer: They may observe different velocities for the same object. Relative motion causes different velocity measurements.

Flashcard 29: What is the formula for velocity addition in one dimension?

Answer: $v' = v + u$. Add the frame velocity $u$ to the object velocity $v$.

Flashcard 30: How does speed differ in different reference frames?

Answer: Speed is frame-dependent and can vary between frames. Different frames measure different speeds for the same object.