Physics Chapter on Motion and Reference Frames
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Questions and Answers

Motion is described with respect to a:

  • Frame of reference (correct)
  • Slope
  • Graph
  • Displacement

    • Displacement is distance combined with:

  • Speed
  • Velocity
  • Direction (correct)
  • Magnitude

    • Displacement vectors of 3 m and 5 m in the same direction combine to make a displacement vector that is:

  • 0 m
  • 8 m (correct)
  • 2 m
  • 15 m

    • Average speed is the total distance divided by the:

    <p>Total time</p> Signup and view all the answers

    The slope of a distance-time graph is equal to the:

    <p>Speed</p> Signup and view all the answers

    Velocity is:

    <p>Speed with direction</p> Signup and view all the answers

    Two or more velocities can be combined by:

    <p>Using vector addition</p> Signup and view all the answers

    A ball just dropped is an example of:

    <p>Free fall</p> Signup and view all the answers

    Acceleration is equal to:

    <p>Change in speed divided by time</p> Signup and view all the answers

    The rate at which velocity is changing at a given instant is described by:

    <p>Instantaneous acceleration</p> Signup and view all the answers

    Why is it necessary to choose a single frame of reference when measuring motion?

    <p>It is the only way to measure motion in a clear and relevant manner.</p> Signup and view all the answers

    For what kinds of distances would you choose to make measurements in millimeters? In kilometers?

    <p>You would measure a very small distance in millimeters and a very large distance in kilometers.</p> Signup and view all the answers

    Light from a star travels to Earth in a straight line at a constant speed of almost 300,000 km/s. What is the acceleration of the light?

    <p>0 km/s/s</p> Signup and view all the answers

    If two displacement vectors add to yield a total displacement of zero, what do you know about the two displacements?

    <p>They are in opposite directions from each other and are the same distance.</p> Signup and view all the answers

    How will the total distance traveled by a car in 2 hours be affected if the average speed is doubled?

    <p>It will also double.</p> Signup and view all the answers

    How do you know that a speedometer tells you the instantaneous speed of a car?

    <p>It tells you the speed that the car is moving at the exact moment in time that you look at it.</p> Signup and view all the answers

    On a distance-time graph, what would the curve describing constant speed look like?

    <p>It would be a straight line.</p> Signup and view all the answers

    A spider is crawling on a wall. First it crawls 1 m up, then 1 m to the left, and then 1 m down. What is its total displacement?

    <p>1 m left</p> Signup and view all the answers

    A jogger travels 8.0 km in 1.25 h. What is the jogger's average speed?

    <p>6.4 km/h</p> Signup and view all the answers

    You see a lightning bolt in the sky. You hear a clap of thunder 3 seconds later. The sound travels at a speed of 330 m/s. How far away was the lightning?

    <p>990 m</p> Signup and view all the answers

    If a river current is 8.0 m/s, and a boat is traveling 10.0 m/s upstream, what is the boat's speed relative to the riverbank?

    <p>2 m/s</p> Signup and view all the answers

    If an object is moving with constant velocity, what do you know about its acceleration?

    <p>It is 0.0 m/s/s.</p> Signup and view all the answers

    If the plotted points on a speed-time graph do not form a straight line, what do you know about the object's acceleration?

    <p>It is not constant.</p> Signup and view all the answers

    Explain a situation in which you can accelerate even though your speed doesn't change.

    <p>You can change the direction of your velocity.</p> Signup and view all the answers

    A girl moves at 2 m/s delivering newspapers. She throws a newspaper directly behind her at 2 m/s. In the frame of reference of someone standing nearby, what is the motion of the newspaper?

    <p>To someone standing directly in front of or behind her, it does not move. To someone standing to the side of her, it moves backward slightly.</p> Signup and view all the answers

    Design an experiment to measure the speed of a toy train going around a circular track.

    <p>Measure the distance of the track. Time the train going around the track exactly 1 time. Divide the distance by the time.</p> Signup and view all the answers

    A raft floats downstream. After 1 minute it has moved 50.0 m. After 2 mins it has moved 100.0 m. After 3 min it has moved 150.0 m. Could the raft's speed be constant? Explain.

    <p>Yes, because it moves another 50.0 m each minute.</p> Signup and view all the answers

    A rocket ship is moving through space at 1000 m/s. It accelerates in the same direction at 4 m/s^2. What is its speed after 100 s?

    <p>1400 m/s</p> Signup and view all the answers

    If a displacement-time graph goes steadily up and then flattens out, describe the history of the motion.

    <p>A person walks at a constant speed, then stops walking.</p> Signup and view all the answers

    If a displacement-time graph goes steadily up to 15 meters at 10 seconds and flattens out, how fast is the person walking during the first 10 s?

    <p>1.5 m/s</p> Signup and view all the answers

    A car starts from rest and increases its speed to 15 m/s in 20 s. What is the car's acceleration?

    <p>0.75 m/s/s</p> Signup and view all the answers

    The propulsion system of a rocket ship moving through space at 1000 m/s with an acceleration rate of 4 m/s/s is tested. Its rockets are fired and the ship accelerates from rest at 5 m/s/s for 2 min. How does the ship's final velocity compare to the initial velocity of the first testing?

    <p>It is less than the initial velocity of the first testing.</p> Signup and view all the answers

    Compare the case of a rubber ball falling through the air and a rubber ball bouncing up and down on a hard floor. For which of these cases is the instantaneous acceleration always the same as the constant acceleration?

    <p>The case of a rubber ball falling through the air.</p> Signup and view all the answers

    Two trains on parallel tracks are traveling in the same direction. One train starts 10 km behind the other. It overtakes the first train in 2 h. What is the relative speed of the second train with respect to the first train?

    <p>5 km/h</p> Signup and view all the answers

    Study Notes

    Motion and Reference Frames

    • Motion is measured relative to a frame of reference, necessary for clear measurements.
    • Velocity is defined as speed with direction.

    Displacement

    • Displacement incorporates distance with direction, crucial for determining overall movement.
    • Displacements can be combined; for instance, a 3 m and 5 m vector in the same direction results in an 8 m vector.

    Speed and Acceleration

    • Average speed is calculated by total distance over total time.
    • Acceleration is defined as the change in speed divided by time, with constant velocity indicating zero acceleration.

    Graph Interpretation

    • The slope of a distance-time graph represents speed; a straight line indicates constant speed.
    • Speed-time graphs that do not form straight lines indicate non-constant acceleration.

    Real-Life Applications

    • An average speed increase results in doubled total distance over the same time span.
    • A situation where speed remains constant but motion changes direction exemplifies acceleration without speed change.

    Measurement and Context

    • Small distances are measured in millimeters, while large distances are measured in kilometers for clarity.
    • Instantaneous speed is observed at a specific moment, such as on a car's speedometer.

    Relative Motion

    • The relative speed of objects, such as trains or boats, can differ based on their respective frames of reference.
    • E.g., a boat moving upstream against a current has a different speed relative to the riverbank compared to its speed in the water.

    Time and Distance Relationships

    • Calculating distance can involve methods like timing an object traveling around a defined path.
    • For example, a light traveling at nearly 300,000 km/s has an acceleration of 0 km/s/s since its speed remains constant.

    Motion in Different Directions

    • Total displacement can vary significantly when moving in multiple directions, exemplified by a spider's movements.
    • A raft that moves consistently downstream can have constant speed, despite the incremental increase in distance over time.

    Velocity and Changes in Speed

    • A rocket's velocity increases due to constant acceleration; comparisons to previous velocities can indicate performance changes.
    • Instantaneous acceleration can differ between actions, such as falling versus bouncing, highlighting different acceleration dynamics based on context.

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    Description

    Test your understanding of motion, reference frames, and key concepts like displacement, speed, and acceleration. This quiz also covers the interpretation of graphs related to distance and speed. Dive into the real-life applications of these fundamental physics concepts!

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