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Ch 03: Motion in Two or Three Dimensions
Chapter 3, Problem 3

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. (b) How high is this point?

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1
Identify the initial vertical velocity component (Vy) which is given as 12.0 m/s.
Use the kinematic equation for vertical motion to find the maximum height. The equation is Vy^2 = 2gH, where Vy is the initial vertical velocity, g is the acceleration due to gravity (approximately 9.8 m/s^2), and H is the maximum height.
Rearrange the equation to solve for H: H = Vy^2 / (2g).
Substitute the values of Vy and g into the equation to find H.
Calculate H using the values Vy = 12.0 m/s and g = 9.8 m/s^2 to find the maximum height the football reaches.

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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 that is launched into the air and is subject to gravitational forces. It can be analyzed in two dimensions: horizontal and vertical. The horizontal motion is uniform, while the vertical motion is influenced by gravity, leading to a parabolic trajectory. Understanding this concept is essential for solving problems involving objects thrown at an angle.
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Kinematic Equations

Kinematic equations describe the motion of objects under constant acceleration, such as gravity. For vertical motion, the key equation is h = v_i * t + 0.5 * a * t^2, where h is height, v_i is the initial vertical velocity, a is acceleration (gravity), and t is time. These equations allow us to calculate various parameters of motion, including maximum height and time of flight.
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Components of Velocity

Velocity can be broken down into horizontal and vertical components, which are crucial for analyzing projectile motion. The initial velocity of the football is given as two components: an upward (vertical) component of 12.0 m/s and a horizontal component of 20.0 m/s. By separating these components, we can independently analyze the vertical motion to determine the maximum height reached by the projectile.
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Related Practice
Textbook Question
A shot putter releases the shot some distance above the level ground with a velocity of 12.0 m/s, 51.0° above the horizontal. The shot hits the ground 2.08 s later. Ignore air resistance. (c) How far did she throw the shot horizontally?
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Textbook Question
In a carnival booth, you can win a stuffed giraffe if you toss a quarter into a small dish. The dish is on a shelf above the point where the quarter leaves your hand and is a horizontal distance of 2.1 m from this point (Fig. E3.19). If you toss the coin with a velocity of 6.4 m/s at an angle of 60° above the horizontal, the coin will land in the dish. Ignore air resistance. (a) What is the height of the shelf above the point where the quarter leaves your hand?

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Textbook Question
In a carnival booth, you can win a stuffed giraffe if you toss a quarter into a small dish. The dish is on a shelf above the point where the quarter leaves your hand and is a horizontal distance of 2.1 m from this point (Fig. E3.19). If you toss the coin with a velocity of 6.4 m/s at an angle of 60° above the horizontal, the coin will land in the dish. Ignore air resistance. (b) What is the vertical component of the velocity of the quarter just before it lands in the dish?

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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. (c) 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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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. (d) How far has the football traveled horizontally during this time?
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Textbook Question
The froghopper, Philaenus spumarius, holds the world record for insect jumps. When leaping at an angle of 58.0° above the horizontal, some of the tiny critters have reached a maximum height of 58.7 cm above the level ground. (See Nature, Vol. 424, July 31, 2003, p. 509.) (a) What was the takeoff speed for such a leap?
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