Algebra 1 Quadratic Functions Part 1: Distance fallen: d(t) = 16t2
Spring 2014
Act 1. Pumpkin Dropping. Complete the table below to show estimates for the pumpkin's distance fallen and
height above ground in feet at various times between 0 and 3 seconds.
Act 2. Use data relating height and time to answer the following questions about flight of a pumpkin
dropped from a position 100 feet above the ground.
a.
What equation shows how the pumpkin's height h is related to time t? _______________________
b.
What equation can be solved to find the time
when the pumpkin is 10 feet above the ground? _______________________________
c.
What is your best estimate for the solution to part b? _______________________
d.
What equation can be solved to find the time when the pumpkin hits the ground? ________________
What is your best estimate for the solution? _______________________
e.
How would your answers to parts a, b, and c change if the pumpkin were to be dropped from a spot 75
feet above the ground?
Act 3. Suppose a pumpkin is fired straight upward from the barrel of a compressed-air cannon at a point 20
feet above the ground, at a speed of 90 feet per second (about 60 mph). For this entire activity, assume that
we have NO gravitational force pulling the pumpkin back toward the ground.
a.
How would the pumpkin's height above the ground change as time passes?
b. What equation would relate height above the ground h in feet to time in the air t in seconds?
c.
How would you change the equation in part b if the punkin'chunker used a stronger cannon that fired
the pumpkin straight up into the air with a velocity of 120 feet per sec?
d. How would you change the equation in part b if the end of the cannon barrel was only 15 feet above the
ground, instead of 20 feet?
Act 4. Now think about how the flight of a launched pumpkin results from the combination of three factors:
Initial height of the pumpkin, initial upward velocity, and gravity pulling the pumpkin down toward the ground.
a.
h(t) = ____________________________
b. h(t) = ____________________________
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Act 5. By now you may have recognized that the height of a pumpkin shot straight up into the air at any
time in its flight will be given by an equation that can be expressed in the general form
h(t) = h0 + v0t – 16t2 In these equations, h is measure in feet and t in seconds.
a.
What does the value of h0 represent? __________________________________________
What units are used to measure h0?
b.
_________________
What does the value of v0 represent? __________________________________________
What units are used to measure v0?
_________________
Act 6.The pumpkin's height in feet t seconds after it is launched will still be given by h(t) = h0 + v0t – 16t2
a.
Suppose that a pumpkin leaves a cannon at a point 24 feet above the ground when t = 0. What does that
fact tell about the equation giving height h as a function of time in flight t?
b.
Suppose you were able to use a stopwatch to discover that the pumpkin shot described in part a
returned to the ground after 6 seconds. Use that information to find the value of v0.
Act 7. One Pumpkin Launch
a.
Plot the data on a graph and experiment with several values of v0 and h0 in search of an equation that
models the data pattern well. What is your equation?
b. Use the quadratic curve-fitting tool (QuadReg) on your calculator to find a quadratic equation for the
sample data pattern. Compare this equation to the one you found with your own experimentation in part a.
c.
Use the equation that you found in part b to write and solve equations and inequalities.
i.
When was the pumpkin 60 feet above the ground?
Equation: __________________________
Solution: ___________________
ii.
For which time(s) was the pumpkin at least 60 feet above the ground?
Equation: __________________________
Solution: ___________________
d.
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Use the equation that you found in part b to answer these questions about the pumpkin shot.
i.
What is your best estimate for the
maximum height of the pumpkin? __________________
ii.
When does the pumpkin reach that height? _____________________
Act 8. Game 3 of the 1970 NBA championship series where Jerry West made his 60 foot shot.
Through careful analysis of the game tape, one could determine the height at which Jerry West released the
ball, as well as the amount of time that elapsed between the time the ball left his hands and the time the ball
reached the basket. This information could then be used to write a rule for the ball’s height h in feet as a
function of time in flight t in seconds.
a.
Suppose the basketball left West's hands at a point 8 feet above the ground. What does that
information tell you about the rule giving h as a function of t?
b. Suppose also that the basketball reached the basket (at a height of 10 ft) 2.5 seconds after it left
West’s hands. Use this information to determine the initial upward velocity of the basketball.
c.
Write a rule giving h as a function of t. ______________________________________
d. Use the equation you developed in part c to write and solve equations and inequalities to answer these
questions about the basketball shot. Be sure to sketch and label the solution on the graph.
i.
At what other time(s) was the ball at the height of the rim (10 ft)?
Equation: ________________________________
Solution: _____________________
ii.
For how long was the ball higher than 30 feet above the floor?
Equation: ________________________________
Solution: _____________________
iii.
If the ball had missed the rim and backboard, when would it have hit the floor?
Equation: ________________________________
Solution: _____________________
e.
What was the maximum height of the shot, and when did the ball reach that point?
Reaction Time Data Collection: The following experiment can be used to measure a person’s reaction time, the amount of time
it takes a person to react to something he or she sees. Hold a ruler at the end that reads 12 inches and let it hang down. Have the
subject hold her or his thumb and forefinger opposite the 0-inch mark without touching the ruler. Tell your subject that you will
drop the ruler within the next 10 seconds and that she or he is supposed to grasp the ruler as quickly as possible after it is dropped.
The spot on the ruler where it is caught indicates the distance that the ruler has dropped.
a.
What equation describes the distance d in feet that the ruler has fallen after t seconds? __________________________
b.
Use what you know about the relationship between feet and inches and your equation from part a to estimate the
reaction time of a person who grasps the ruler at the 4-inch mark.
c.
Conduct this experiment several times and estimate the reaction times of your subjects.
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