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Negative (Downward) Launch quiz

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  • When an object is launched downward, what is always true about its initial velocity in the y-direction?
    The initial velocity in the y-direction (V_{Ay}) is always negative because downward is defined as the negative direction.
  • What is the first step in solving a downward launch projectile motion problem?
    The first step is to draw the scenario, labeling the path and points of interest such as the launch point and where the object lands.
  • How do you determine the height of the building in a downward launch problem?
    The height of the building is the absolute value of the vertical displacement (|Δy|) from the launch point to the ground.
  • What trigonometric function is used to find the initial velocity component in the y-direction?
    The sine function is used: V_{Ay} = V_A * sin(θ), where θ is the angle below the horizontal.
  • How do you calculate the initial velocity component in the x-direction for a downward launch?
    Use the cosine function: V_{Ax} = V_A * cos(θ), with θ as the angle below the horizontal.
  • If you get stuck solving for a variable in one axis, what should you do?
    Switch to the other axis and use its equations to solve for additional variables, such as time.
  • What equation relates horizontal displacement, velocity, and time in projectile motion?
    Δx = V_{Ax} * Δt, where Δx is horizontal displacement, V_{Ax} is horizontal velocity, and Δt is time.
  • Why is the acceleration in the y-direction negative in these problems?
    Because acceleration due to gravity acts downward, it is assigned a value of -9.8 m/s².
  • Which kinematic equation is used when the final velocity is unknown?
    The equation Δy = V_{Ay} * Δt + (1/2) * a_y * (Δt)^2 is used when the final velocity is not known.
  • How do you find the time the object spends in the air using horizontal motion?
    Divide the horizontal distance by the horizontal velocity: Δt = Δx / V_{Ax}.
  • What is the calculated time of flight for a rock thrown downward at 5 m/s at 37° below horizontal, landing 10 m away?
    The time of flight is 2.5 seconds.
  • What is the calculated vertical displacement (Δy) for the example problem in the video?
    The vertical displacement is -38.1 meters.
  • Why do we take the absolute value of vertical displacement to find the building's height?
    Because height is always a positive quantity, so we use |Δy|.
  • How do you calculate the magnitude of the velocity just before the object hits the ground?
    Use the Pythagorean theorem: v = sqrt(V_{Bx}^2 + V_{By}^2).
  • How is the direction of the velocity before impact expressed, and what does a negative angle indicate?
    The direction is found using the inverse tangent function, and a negative angle indicates the direction is below the x-axis.