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Ignore air resistance. The coyote's next scheme involves launching himself into the air with an Acme catapult. If the coyote is propelled vertically from the ground with initial velocity \(64 \mathrm{ft} / \mathrm{s}\), find an equation for the height of the coyote at any time \(t .\) Find his maximum height, the amount of time spent in the air and his velocity when he smacks back into the catapult.

Short Answer

Expert verified
The equation for the coyote's height is given by \(h = 64t - 16t^2\). The coyote reaches a maximum height of 64 ft, spends 4s in the air and smacks back into the ground at a velocity of -64 ft/s.

Step by step solution

01

Formulate the height equation

The height \(h\) at any time \(t\) can be given by the equation \(h = ut - 0.5gt^2\), where \(u\) is the initial velocity and \(g\) is the acceleration due to gravity (32 ft/s²). Substituting the given initial velocity in the equation, we have: \(h = 64t - 0.5*32t^2 = 64t - 16t^2\)
02

Calculate the maximum height

Noting that at the maximum height, velocity == 0. Hence we calculate the time when velocity becomes zero and substitute it into our height equation. The velocity \(v = u - gt\). Equating \(v = 0\) and solving for \(t\) gives \(t = 64/32 = 2s\). Substituting \(t = 2\) in our height equation, we get: \(h_{max} = 64*2 - 16*2^2 = 64 ft\)
03

Find the time spent in the air

The time spent in the air is twice the time spent to reach maximum height, therefore \(t_{air} = 2 * t_{max height} = 2 * 2 = 4s\).
04

Calculate the velocity upon landing

At this point the coyote's velocity will be his final velocity which is given by \(v = u - gt\). Therefore \(v_{landing} = 64 - 32*4 = -64 ft/s\). The negative sign indicates that the velocity is directed downwards.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Initial Velocity
Understanding the initial velocity of an object is crucial when studying projectile motion. It is the speed at which an object is launched into motion. As seen in the coyote's escapade with the Acme catapult, the initial velocity, denoted by 'u', is set at 64 ft/s. In mathematical terms, when the coyote begins his flight, the influence of gravity hasn't started affecting his ascent yet; hence the initial velocity is the highest at this point. It's important to note that the initial velocity has both magnitude (speed) and direction, which in this case is purely vertical.

For projectile motion, the initial velocity is what determines the overall trajectory along with other factors like gravity. It is the baseline for calculating various other aspects of the motion, such as the maximum height reached and the time of flight. Understanding the initial velocity allows us to study the coyote's endeavor further, predicting the height at different time intervals until he reaches the zenith of his ascent.
Maximum Height
The maximum height of a projectile is the highest vertical position it reaches during flight. This point is crucial because it's where the upward motion pauses before succumbing to gravity's pull back to the ground. In projectile motion equations, the time at maximum height corresponds to the situation where the vertical velocity becomes zero. This happens because gravity has slowed down the initial upward momentum to a halt (this is also where the velocity v equals zero, as seen in the coyote's calculation).

In the coyote's attempt to reach for the sky via catapult, he achieves a maximum height – denoted as \(h_{max}\) – of 64 feet. This is figured out by substituting the time taken to reach this point, found by setting the velocity equation to zero, back into the height equation. This peak point is not only a pinnacle in his trajectory but also pivotal for calculating his time in the air and eventual velocity upon landing.
Time of Flight
The time of flight in projectile motion refers to the total duration an object remains airborne. It starts from the moment of launch to the moment it returns to the launch elevation. For the coyote's adventure, his time in the air is dependent on his initial velocity and the acceleration due to gravity. It's intuitive to think that the coyote's time of flight would be the moment he reaches the maximum height, but that's just the halfway mark.

The total time of flight is actually twice the time it takes to reach max height, because what goes up must come down, and it takes just as long to return to the ground (ignoring air resistance). In our case, since it takes the coyote 2 seconds to reach his maximum altitude, his total time of flight ('t_air') is 4 seconds. This entire period defines the whole dramatic arc of the coyote's journey – from the initial launch to his inevitable descent back to the catapult.
Acceleration Due to Gravity
Acceleration due to gravity, commonly denoted by 'g', is the constant rate at which objects accelerate towards Earth when in free fall. This acceleration is approximately 32 ft/s² in our coyote's story. Gravity is a key force in projectile motion, countering initial velocity and pulling the coyote back toward the ground after the launch.

During his aerial escapade, gravity acts uniformly at every instant, shaping the parabolic path of his flight. As he ascends, it slows him down until he reaches the maximum height, and as he descends, it accelerates him back to his starting point. The role of gravity is apparent also in calculating the final landing velocity (which we found to be -64 ft/s), indicating a downward motion, and emphasizes the symmetry of his time in the air, as it defines both rise and fall durations equally.

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Most popular questions from this chapter

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