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Algebra 1

7.6.2 The Force of Gravity Change in Quadratic Functions

Algebra 17.6.2 The Force of Gravity Change in Quadratic Functions

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Activity

Earlier, in activity 7.6.1, you completed a table that represents the height of a cannonball, in feet, as a function of time, in seconds, if there was no gravity.

This table shows the actual heights of the ball at different times.

Seconds 0 1 2 3 4 5
Distance above ground (feet) 10 400 758 1084 1378 1640

1. Compare the values in this table with those in the table you completed earlier. What are two similarities or differences that you notice?

2. Use the graphing tool or technology outside the course.

a. Plot the two sets of data you have on the same coordinate plane.

b. How are the two graphs alike? How are they different?

3. What is the starting position for both graphs?

4. What was the constant rate of change for the cannonball without gravity?

The constant rate of change is also the initial velocity. Recall that the effect of gravity is represented by 16 t 2 16 t 2 . Gravity causes the bend in the curve for the second table and graph because it pulls the cannonball down toward the ground.

5. With a partner, write an equation to model the actual distance d d , in feet, of the ball t t seconds after it was fired from the cannon. Consider gravity and how the points changed on the graph.

Self Check

An arrow is shot up into the air from 5 feet, at an initial velocity of 220 feet per second. Which equation can represent the height, h ( t ) , for any time, t ?
  1. h ( t ) = 220 + 5 t 16 t 2
  2. h ( t ) = 5 + 220 t 16 t 2
  3. h ( t ) = 5 + 220 t + 16 t 2
  4. h ( t ) = 5 + 220 t

Additional Resources

The Effect of Gravity on Motion

A firework is sent up in the air, at an initial velocity of 130 feet per second, from a height of 6 feet. Write an equation that represents the height, h ( t ) h ( t ) , of the firework for any second, t t . Remember to consider the effect of gravity.

Step 1 - Identify the initial velocity, v 0 v 0 .

130 ft per second

Step 2 - Identify the starting height, h 0 h 0 .

6

Step 3 - Write an equation of this form: h ( t ) = h 0 + v 0 t 16 t 2 h ( t ) = h 0 + v 0 t 16 t 2 .

h ( t ) = 6 + 130 t 16 t 2 h ( t ) = 6 + 130 t 16 t 2

Try it

Try It: The Effect of Gravity on Motion

Write an equation if a firework is shot from 2 feet off the ground at an initial velocity of 110 feet per second. Write an equation that represents the height, h ( t ) h ( t ) , of the firework for any second, t t . Remember to consider the effect of gravity.

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