General Physics 1 Unit 4: Motion in Two Dimensions
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Questions and Answers

What effect does the moving sidewalk have on Mia's overall speed during the race?

  • It doubles her speed during the race.
  • It keeps her speed constant at 5 m/s.
  • It adds to her speed by 2 m/s. (correct)
  • It decreases her speed by 2 m/s.

How does Brandi's speed compare to Mia's effective speed on the moving sidewalk?

  • Brandi and Mia move at the same speed.
  • Brandi is slower than Mia by 2 m/s.
  • Mia is faster than Brandi by 2 m/s. (correct)
  • Mia is slower than Brandi by 2 m/s.

In the context of the race, what defines relative velocity?

  • The average speed of objects in a race.
  • The speed of one object in relation to another object. (correct)
  • The speed of an object without considering other objects.
  • The speed of an object measured from a stationary point.

What is the primary factor that determines the winner of the race?

<p>The effective speed of each runner. (D)</p> Signup and view all the answers

If Mia had run on a non-moving floor like Brandi, what impact would it have on the race outcome?

<p>Brandi would have an advantage and likely win. (A)</p> Signup and view all the answers

What could Brandi do differently to potentially win the race?

<p>Use a moving sidewalk for herself. (D)</p> Signup and view all the answers

What is the speed at which Mia effectively moves when running on the moving sidewalk?

<p>7 m/s (A)</p> Signup and view all the answers

If the moving sidewalk speed were increased to 4 m/s, what would Mia's new effective speed be?

<p>9 m/s (B)</p> Signup and view all the answers

What does relative velocity refer to?

<p>The velocity of an object observed from another object. (C)</p> Signup and view all the answers

In the relative velocity equation, how is the object reference treated when moving in the opposite direction?

<p>It's assigned a negative value. (B)</p> Signup and view all the answers

Which of the following describes relative velocity in one dimension?

<p>Motions can occur in three possible linear directions. (C)</p> Signup and view all the answers

What must the first subscript in the relative velocity variable represent?

<p>The velocity of the object being observed. (C)</p> Signup and view all the answers

What happens to the subscripted velocities based on the frame of reference?

<p>They indicate different velocities based on the observer's position. (C)</p> Signup and view all the answers

When an object A is moving east at 15 m/s relative to an observer on the Earth's surface, how is its velocity represented?

<p>15 m/s east. (D)</p> Signup and view all the answers

Which of the following is NOT a potential direction of motion in relative velocity in one dimension?

<p>Diagonal direction (C)</p> Signup and view all the answers

What characterizes the resultant velocity of multiple objects in relative velocity?

<p>It is the summation of all vectors involved. (B)</p> Signup and view all the answers

What does the formula for relative velocity in one dimension help to solve for?

<p>The speed of Object A relative to Object B (C)</p> Signup and view all the answers

Which theorem is used to compute the resultant velocity in the formula for relative velocity in two dimensions?

<p>The Pythagorean theorem (B)</p> Signup and view all the answers

In the context of relative velocity, what does vAB represent?

<p>The relative velocity of Object A compared to B (D)</p> Signup and view all the answers

What is the relative velocity of the box of pencils with respect to the box of marbles?

<p>0 mph (A)</p> Signup and view all the answers

When calculating relative velocity in two dimensions, what can be inferred about the motion of Objects A and B?

<p>Their paths must be perpendicular. (D)</p> Signup and view all the answers

What is vA in the context of relative velocity formulas?

<p>The observed object's velocity (C)</p> Signup and view all the answers

If George rides the escalator at a velocity of 0.06 mph, what is Anna's velocity with respect to George's if they are on the same escalator?

<p>0 mph (D)</p> Signup and view all the answers

Which of the following statements best describes the purpose of relative velocity formulas?

<p>To find how fast one object moves in comparison to another (B)</p> Signup and view all the answers

What is the velocity of the second car if the yellow cab's velocity is 29 mph and the relative velocity of the second car is 4 mph?

<p>–25 mph (D)</p> Signup and view all the answers

In a situation where Objects A and B are moving at right angles to each other, which formula should be used to find the relative velocity?

<p>Pythagorean theorem for velocities (B)</p> Signup and view all the answers

What technique is used to determine the velocity of the second car relative to the yellow cab?

<p>Subtracting the relative speed from the cab's speed (B)</p> Signup and view all the answers

Which of the following can be concluded if the relative velocity vAB is zero?

<p>Objects A and B are moving at the same velocity. (D)</p> Signup and view all the answers

In the example with the motorboat and river current, what is the motorboat's velocity in relation to the riverbank?

<p>7 m/s northeast (C)</p> Signup and view all the answers

What does a negative velocity indicate in the context of the second car's velocity?

<p>The second car is moving in the opposite direction relative to the cab (C)</p> Signup and view all the answers

What equation would you likely use to calculate the velocity of the cabin cruiser relative to the man running after it?

<p>Relative Velocity = Velocity of Cruiser - Velocity of Man (B)</p> Signup and view all the answers

If a motion problem provides velocities in different directions, what must be considered to find the total velocity?

<p>The angles of the velocities must be factored (A)</p> Signup and view all the answers

What is the resultant velocity of an airplane traveling south at 113 km/hr with a side wind of 22 km/hr?

<p>115.12 km/hr (A)</p> Signup and view all the answers

Which equation is used to calculate the magnitude of the resultant velocity when dealing with velocities at right angles?

<p>v = √(a^2 + b^2) (A)</p> Signup and view all the answers

How is the direction of the relative velocity determined?

<p>Using the tangent function (C)</p> Signup and view all the answers

What is the velocity of the box of pencils relative to the box of marbles on a conveyor belt moving at 0.059 mph?

<p>0 mph (D)</p> Signup and view all the answers

Which of the following best describes the process to identify resultant velocity when two vectors are perpendicular?

<p>Use the vector sum and apply the Pythagorean theorem (C)</p> Signup and view all the answers

What is the angle produced when calculating the direction of the airplane's relative velocity under side winds?

<p>11 degrees (B)</p> Signup and view all the answers

What happens to the velocity of an object placed on a moving conveyor belt in terms of its relative velocity to the belt?

<p>It becomes 0 mph if at rest on the belt (C)</p> Signup and view all the answers

Which condition must be true for the Pythagorean theorem to be applied in relative velocity calculations?

<p>Vectors must be perpendicular (A)</p> Signup and view all the answers

What is the relative velocity of the first train from the perspective of the second train?

<p>-1 m/s (A)</p> Signup and view all the answers

How does the motion of the first train appear from the second train's frame of reference?

<p>It appears to be moving in the opposite direction. (A)</p> Signup and view all the answers

What must be true for the reference frame when considering relative velocity?

<p>It must always have a constant velocity. (C)</p> Signup and view all the answers

If you are walking east at 12 m/s, what is your velocity relative to a train moving at 27 m/s in the same direction?

<p>15 m/s (A)</p> Signup and view all the answers

Why is it important to consider frame of reference when discussing velocities?

<p>Different observers can perceive different velocities. (D)</p> Signup and view all the answers

What does the negative value in relative velocity signify?

<p>The object has moved away from the observer. (C)</p> Signup and view all the answers

If the first train is moving at 16 m/s west and the second train is moving at 27 m/s east, what is the net velocity of the first train relative to the second train?

<p>11 m/s west (B)</p> Signup and view all the answers

Which of the following statements about relative velocity is true?

<p>Relative velocity can change depending on the observer's motion. (D)</p> Signup and view all the answers

Flashcards

Relative Velocity

Velocity of an object as observed from a particular frame of reference.

Moving Sidewalk

A moving surface that affects the apparent velocity of a person walking on it.

Mia's Velocity

The speed at which Mia is moving relative to the moving sidewalk.

Brandi's Velocity

The speed at which Brandi is moving relative to the stationary ground.

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Relative Velocity in 1D

Calculating the velocity of one object relative to another moving in a straight line.

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Relative Velocity Race

A simulation demonstrating how relative velocity influences perceived motion.

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Race Winner

The runner who completes the race in the least amount of time relative to their starting position.

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Two-Dimensional Relative Velocity

Calculating velocity when the objects are moving in multiple directions (not just forward/backward).

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Relative Velocity

The velocity of an object from the frame of reference of another object or observer. It's the difference in velocity between two objects.

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Relative Velocity Formula

The formula for calculating relative velocity. It's the vector difference between the two velocities.

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Opposite Direction in Relative Velocity

When objects are moving in opposite directions, the velocity of one object relative to another is the sum of the velocities.

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Relative Velocity in 1D

Relative velocity in a straight line. Motions along a straight line have only three possible directions: same, towards, and opposite.

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Frame of Reference

The object or observer used to determine the velocity of another object relative to it. It's the perspective viewpoint

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Subscripts in Relative Velocity

The subscripts in relative velocity variables, like va/b, indicate the object whose velocity is being measured (first subscript) and the frame of reference (second subscript).

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va/b

Velocity of object A relative to object B.

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15 m/s east

Example of a velocity of a train relative to the Earth

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Relative Velocity

Velocity of an object observed from another moving reference point

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Reference Frame

A frame of reference is a coordinate system used to describe the position and motion of objects.

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Velocity of Train

How fast and in what direction a train is moving

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Negative Velocity

Velocity in the opposite direction of the reference frame, used in relative velocity calculation

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Constant Velocity

An object is moving at a fixed speed and in a fixed direction

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One-Dimensional Motion

Motion along a straight line

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Velocity Change

How velocity changes depending on the viewpoint which observes the object in movement

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Frame of Reference

A coordinate system used to describe the motion of an object.

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Relative Velocity (2D)

Velocity of one object as observed from another object's frame of reference in two dimensions.

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Resultant Velocity

The overall velocity of an object when multiple velocities act on it, calculated by vector addition.

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Vector Addition

Combining velocities by adding their vector components to produce a resultant vector.

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Pythagorean Theorem

Used to find the magnitude of resultant velocity when the velocities are at right angles (perpendicular).

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Tangent Function

Used to calculate the direction of the resultant velocity in two dimensions.

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Perpendicular Velocities

Velocities acting at right angles to each other.

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Example 1 (Conveyor Belt)

Relative velocity between moving objects (e.g., box of pencils on a conveyor belt relative to a box of marbles on the same conveyor belt. This is still zero.

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Velocity Calculation

Determine the velocity using the vector sum of velocities under consideration.

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Relative Velocity (1D)

Velocity of one object as observed from another object moving in a straight line.

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Relative Velocity

The velocity of one object as seen by another object.

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Relative Velocity Example: Cab & Car

A car appears to move slower (or faster, depending on direction) to a person in a moving yellow cab. The 'relative' velocity describes this perceived speed.

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Relative Velocity (2D)

Velocity of one object as observed from another object moving in two dimensions (different directions).

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1-D Relative Velocity

Relative velocity calculation for objects moving in a straight line. Either in the same, opposite, or towards each other.

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1D Relative Velocity Formula

vAB = vA - vB (where vAB is relative velocity of object A compared to object B; vA is speed of object A, vB speed of B).

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2D Relative Velocity Formula

Use Pythagorean Theorem to find the resultant velocity of objects moving in two dimensions.

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Vector Difference in Relative Velocity

Determine the relative velocity using vector subtraction of velocities.

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Frame of Reference

The object or viewpoint from which velocity is measured.

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Velocity of Second Car

Calculating the velocity of a car overtaking another.

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Relative Velocity Formula

The calculation of the velocity of an object relative to another by subtracting the velocities.

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vAB

Velocity of object A relative to object B.

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Velocity Relative to a person

Determine the relative speed of something from a stationary observer's perspective.

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Velocity

Speed with direction.

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Motion in Two Dimensions

Calculating the velocity of an object while taking into account multiple directions of movement.

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Pythagorean Theorem

Formula to find the hypotenuse of a right triangle (sum of squares of legs equals square of hypotenuse).

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Study Notes

General Physics 1, Unit 4: Motion in Two Dimensions, Lesson 4.1

  • Motion Descriptors in Two Dimensions: Motion is relative to a specific frame of reference. Relative velocity takes into account the various frames of reference.
  • Learning Objectives: Students should be able to explain relative velocity, solve for relative velocity in one dimension, and solve for relative velocity in two dimensions.
  • Warm Up (Relative Velocity Race): This involves a simulation where two women (Mia and Brandi) compete in a race, one on a moving sidewalk and the other on a stationary floor.
  • Materials: Relative velocity race simulation and pen and paper.
  • Procedure: The simulation involves setting the speed of the moving sidewalk and the speeds of Mia and Brandi. The simulation is run by clicking "Play".
  • Relative Velocity in One Dimension: Relative velocity considers individual motions across a straight line, including the same direction, towards each other, and opposite directions.
  • Position of the Point Object: Visualizing the motion of objects and arranging subscripts (e.g., UAB for velocity of A relative to B) is important. The first subscript represents the observed object; the second is the reference point.
  • Solving Relative Velocity in 1D In a 1D example, a person inside a train moving relative to the ground with a velocity. If a person in the train walks forward at a velocity , the person's velocity relative to the ground is the sum of their velocity on the train and the train's velocity.
  • Relative Velocity in Two Dimensions. Objects can change direction, like airplanes in side winds. The resultant velocity is calculated with the Pythagorean theorem when the velocities are perpendicular.
  • Key Formulas: Relevant formulas for calculating relative velocity in both one and two dimensions are provided, including the Pythagorean theorem to calculate the magnitude of the resultant velocity in two dimensions.
  • Guide Questions: Questions about relative velocity scenarios.
  • Relative Velocity in Two Dimensions. Explains how to solve for situations like airplanes in sidewinds.
  • Key Points: Relative velocity is velocity of an object from another observer's frame of reference. It can be calculated in one or two dimensions, using relevant formulas.
  • Let's Practise Example 1: A problem about the relative velocity of boxes of pencils and marbles on a conveyor belt. The solution shows how to identify what is required and the given, write the working equation, substitute values, to finally calculate the answer (solution 0 mph).
  • Let's Practise Example 2: A problem involves a yellow cab overtaking another car where you must calculate the second car's velocity based on the relative velocity given .
  • Try It Example 1 (Easy): George rides an escalator while Anna rides the same escalator. The question is to find Anna's velocity relative to George.
  • Try It Example 2 (Average): Similar to the example above but slightly different given.
  • Try It Example 3 (Difficult): A motorboat traveling north in a river with a current moving east. What is the motorboat's velocity relative to an observer on the riverbank.
  • Key Formulas: Includes formulas for relative velocity in one and two dimensions, along the direction calculations such as tan θ = opposite/adjacent.
  • Check Your Understanding: A series of questions to test the student's knowledge of the concept of relative velocity.
  • Bibliography: A compilation of resources and textbook references.
  • Challenge Yourself: Further conceptual problems to help students apply their understanding.
  • Key to Try It! Answers to the practice problems.

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Motion in Two Dimensions PDF

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Explore the concepts of motion in two dimensions through the lens of relative velocity. This quiz will help you understand how different frames of reference affect motion, along with practical applications involving simulations. Get ready to correlate theoretical and practical aspects of motion with engaging activities.

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