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Ch 03: Motion in Two or Three Dimensions
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 3, Problem 12b

A rookie quarterback throws a football with an initial upward velocity component of 12.0 m/s and a horizontal velocity component of 20.0 m/s. Ignore air resistance. How high is this point?

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1
Identify the vertical motion of the football. The initial upward velocity component is given as 12.0 m/s. This is the initial velocity in the vertical direction.
Use the kinematic equation for vertical motion to find the maximum height. The equation is: vf=vi+at, where vf is the final velocity (0 m/s at the peak), vi is the initial velocity (12.0 m/s), a is the acceleration due to gravity (-9.8 m/s²), and t is the time to reach the peak.
Solve for the time t it takes to reach the peak using the equation: t=-via. Substitute the values to find t.
Use the kinematic equation for displacement to find the maximum height: h=vit+12at2. Substitute the values of vi, t, and a to find h.
Interpret the result: The calculated height is the maximum height reached by the football during its flight, considering only the vertical motion and ignoring air resistance.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Projectile Motion

Projectile motion refers to the motion of an object thrown or projected into the air, subject to only the acceleration of gravity. It involves two components of motion: horizontal and vertical. The horizontal motion is constant, while the vertical motion is influenced by gravity, causing the object to follow a parabolic trajectory.
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Introduction to Projectile Motion

Kinematic Equations

Kinematic equations describe the motion of objects in terms of displacement, velocity, acceleration, and time. For vertical motion under gravity, the equation h = v_i*t + 0.5*a*t^2 can be used, where h is the height, v_i is the initial vertical velocity, a is the acceleration due to gravity, and t is the time. These equations help calculate the maximum height reached by the projectile.
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Vertical Motion under Gravity

Vertical motion under gravity is characterized by a constant acceleration downwards, typically 9.8 m/s² on Earth. When an object is projected upwards, it will decelerate until it reaches its peak height, where the vertical velocity becomes zero. Understanding this concept is crucial for determining the maximum height of a projectile.
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Related Practice
Textbook Question

A rookie quarterback throws a football with an initial upward velocity component of 12.0 m/s and a horizontal velocity component of 20.0 m/s. Ignore air resistance. How much time (after it is thrown) is required for the football to return to its original level? How does this compare with the time calculated in part (a)?

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A rookie quarterback throws a football with an initial upward velocity component of 12.0 m/s and a horizontal velocity component of 20.0 m/s. Ignore air resistance. How far has the football traveled horizontally during this time?

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A rookie quarterback throws a football with an initial upward velocity component of 12.0 m/s and a horizontal velocity component of 20.0 m/s. Ignore air resistance. How much time is required for the football to reach the highest point of the trajectory?

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