Lecture 1 Chapter 1: Gravitational Forces and Acceleration
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Questions and Answers

What is the direction of the acceleration aR of a mass on the surface of the earth?

  • Perpendicular to the earth's surface
  • Away from the center of the earth
  • Parallel to the earth's surface
  • Toward the center of the earth (correct)

    • What is the value of acceleration due to gravity on the surface of the earth?

  • 10 ms-2
  • 9.5 ms-2
  • 9.8 ms-2 (correct)
  • 9.2 ms-2

    • What is the force acting on a mass at the surface of the earth?

  • FG only
  • FG + w
  • w only
  • FG - w (correct)

    • Where is the value of g equal to GME/R2?

    <p>At the poles</p> Signup and view all the answers

    What is the effect of the earth's rotation on the weight of an object?

    <p>It decreases the weight</p> Signup and view all the answers

    What is the expression for the acceleration due to gravity on the earth's surface?

    <p>GMe/R2</p> Signup and view all the answers

    What is the magnitude of the resistive force expressed as?

    <p>1/R = DAρv^2/2</p> Signup and view all the answers

    What is the value of the drag coefficient for spherical objects?

    <p>0.5</p> Signup and view all the answers

    What is the net force acting on an object released from rest?

    <p>Fg - R</p> Signup and view all the answers

    What is the acceleration of the object when it reaches terminal speed?

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

    What is the terminal velocity of a spherical water droplet with a radius of 5 microns in still air?

    <p>3 × 10^(-3) m/s</p> Signup and view all the answers

    What is the direction of the actual direction at other locations with respect to the earth's axis of rotation?

    <p>Perpendicular to the earth's axis of rotation at the given latitude</p> Signup and view all the answers

    What is the dynamic viscosity of air at 20°C?

    <p>1.8 × 10^(-5) kg/m · s</p> Signup and view all the answers

    What is the terminal speed of an object in terms of its mass and other parameters?

    <p>v_T = sqrt(2mg/ρDA)</p> Signup and view all the answers

    Why does the baseball strike the ground first in the quiz?

    <p>Because it has a smaller cross-sectional area</p> Signup and view all the answers

    What is the value of g in m/s2, approximately, according to the calculation?

    <p>0.0337</p> Signup and view all the answers

    What is the density of water in kg/m³?

    <p>1000 kg/m³</p> Signup and view all the answers

    What is the period of the rotation of the earth in seconds?

    <p>8.64 × 10^4 s</p> Signup and view all the answers

    What is the time at which the sphere reaches a speed of 0.900 vT?

    <p>11.7 ms</p> Signup and view all the answers

    What is the model of resistive force applicable to objects moving at high speeds through air?

    <p>Resistive force proportional to object speed squared</p> Signup and view all the answers

    In which situation is the resistive force assumed to be proportional to the speed of the moving object?

    <p>For objects falling slowly through a liquid and for very small objects, such as dust particles, moving through air</p> Signup and view all the answers

    What is the radius of the spherical water droplet in the example?

    <p>5 microns</p> Signup and view all the answers

    What is the expression for the resistive force, R, if it is proportional to the object's velocity?

    <p>R = -bv</p> Signup and view all the answers

    What is the dependence of the resistive force on the speed of the moving object for large objects, such as a skydiver moving through air?

    <p>It is proportional to the square of the speed of the moving object</p> Signup and view all the answers

    A baseball is thrown with a speed of 40.2 m/s. What is the primary factor that affects the resistive force acting on the ball?

    <p>Cross-sectional area of the ball</p> Signup and view all the answers

    What is the terminal velocity of a 75 kg skydiver descending head first with a cross-sectional area of approximately 0.18m²?

    <p>350km/h</p> Signup and view all the answers

    What is the Resistive force acting on a 0.145-kg baseball thrown at 40.2 m/s?

    <p>1.2 N</p> Signup and view all the answers

    What is the primary purpose of finding the terminal velocity of an object?

    <p>To determine the resistive force acting on the object</p> Signup and view all the answers

    What is the unit of the drag coefficient?

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

    What is the relation between the resistive force and the speed of an object?

    <p>The resistive force is proportional to the square of the speed of the object</p> Signup and view all the answers

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