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Name: ___________________________ DUE: Friday 9/18 PELLICCIO/AP PHYSICS

EDUCATION IS FREEDOM! HOMEWORK

HW UNIT 1 1.10

Directions: Take Cornell Notes on the attached textbook copy (your notes need not exceed one page). Then answer the questions in the problem set that follows. Turn only the first page to the HW folder. _________________________________________________________________________________________________________________________________________________

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PROBLEM SETUse the website below for Part I. This is the same website we worked on during class. Remember you have until Friday to complete this problem set, so you must be able to obtain access to computer by then!

http://www.physicsclassroom.com/Physics-Interactives/Vectors-and-Projectiles/Projectile-Simulator

PART I:

A. For each of the questions below, select your answer and explain how you know.

1. How does the initial horizontal velocity (right after it starts moving) compare to the final horizontal velocity (just before hitting the ground)?a. They are equal b. They initial is greater c. The final is greater

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2. How does the initial vertical velocity (right after it starts moving) compare to the final vertical velocity (just before hitting the ground)?a. They are equal b. The initial is greater c. The final is greater

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3. Acceleration involves a change in speed. In which direction does a projectile accelerate?a. Horizontally only b. Vertically only c. Both horizontally and vertically

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4. Run several trials to fill in the table below. Remember to use the arrows at the top to step through the motion.

Trial Speed (m/s) Time of Flight (s) Horizontal Displacement (m)

Maximum Vertical Displacement (m)

1 10

2 20

3 30

4 40

5 60

Use the data above to answer the next set of questions:

5. Describe the effect that increasing launch speed has upon the time of flight.



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6. Describe the effect that increasing launch speed ahs upon the horizontal displacement. _______________________________________________________________________________________________________________________________________

7. A doubling of launch speed causes the time of flight to ______ and the x-displacement to ______. a. double; doubleb. halve; doublec. not change; doubled. double; not changee. double; halvef. not change; halve

8. Which two trials could be used to show the effect that a tripling of the launch speed has on the time and the x-displacement? a. Trials 1 and 2b. Trials 2 and 4c. Trials 2 and 5

9. Experiment with the Interactive in order to determine what changes must be made in order to decrease the time to fall. Describe what you changed, what you observed, and what you conclude:

What I changed:_______________________________________________________________________________________________________________________________________

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What I observed:_______________________________________________________________________________________________________________________________________

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What I conclude regarding what changes must be made to decrease the time to fall:_______________________________________________________________________________________________________________________________________

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10. Now run a few trials again and observe the vertical velocity vector as the projectile approaches its highest point. At its highest point what is the vertical velocity? Explain how you know using scientific principles. _______________________________________________________________________________________________________________________________________

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11. Compare the time it takes for the projectile to reach its peak height and the time it takes the projectile to fall from the peak height to the ground. _______________________________________________________________________________________________________________________________________

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12. A student makes the following claim: “The vertical velocity (vy) 1.0 second before reaching the peak is the same size as the vertical velocity (vy) 1.0 second

after reaching the peak. The same is true of the vy values 2.0 seconds before and after the peak.”

a. Do you agree or disagree with this student’s claim? _____________________b. Explain. Run a few simulations and provide concrete evidence for your answer.

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13. Complete a set of trials to fill in the table below:

Trial Angle (°) Time of Flight (s)Horizontal

Displacement (m)Vertical Displacement

(m)

1 15

2 25

3 35

4 40

5 45

6 50

7 55

8 65

9 75

14. What launch angle results in the greatest range? What launch angle results in the greatest maximum height? Explain using evidence. _______________________________________________________________________________________________________________________________________

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15. State a rule that describes what pair of launch angles could be expected to result in the same x-displacement (range). Use evidence to support this rule. _______________________________________________________________________________________________________________________________________

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PART II: Show all work for these practice problems. The type of questions you will see on the test are similar to those in the medium or hard category.

EASY: 1. Two campers in a national park hike from their cabin to the same spot on a lake, each taking a different path, as

illustrated below. The total distance traveled along Path 1 is 7.5 km, and that along Path 2 is 8.2 km. What is the final displacement of each camper?

2. During a lecture demonstration, a professor places two coins on the edge of a table. She then flicks one of the coins horizontally off the table, simultaneously nudging the other over the edge. Describe the subsequent motion of the two coins, in particular discussing whether they hit the floor at the same time.

3. For a launch speed of 25 m/s, what launch angle will result in the same range as a projectile launched at an angle of 30°?

MEDIUM: 4. A projectile is launched at an angle above the ground. The horizontal component of the projectile’s velocity is initially

40 m/s. The vertical component of the projectile’s velocity is initially 30 m/s. What are the components of the projectile’s velocity after 2 seconds of flight?



5. A truck and a sports car are side by side at one end of a long straight road. The truck starts from rest at t=0 seconds

and accelerates at 1.50m/s2. The sports car starts from rest at t=8.00 s and accelerates at 3.50m/s2. (a) At what time is the sports car’s speed equal to the truck’s? (b) What is that speed? (c) At what time are they side by side again? (d) How far have they traveled when they are again side by side?

6. Maks stands at the top of a cliff that is 80.0m high. He drops one rock (initial speed is 0m/s) and picks up another rock in time to throw it downward 2.00 seconds later with a certain non-zero initial speed. The two rocks hit the ground below the cliff at exactly the same time. With what initial speed did Maks thrown the second rock?

7. Suppose that the football kicked by a place-kicker travels as a projectile (i.e., without air resistance). It is kicked with a speed of 25.0 m/s at a 30° angle. It must pass over field goal posts that are approximately 3 meters high. What would be the maximum field goal distance that could be kicked?

8. The free fall trajectory of an object thrown horizontally from the top of a building is shown as the dashed line in the figure. Which sets of arrows best correspond to the directions of the velocity and of the acceleration for the object at the point labeled P on the trajectory? Why?

HARD:



9. Prove that the trajectory of a projectile is parabolic, having the form y=ax+b x2. To obtain this expression, solve the

equation x=v0x t for t and substitute it into the expression for y=v0 y t−12¿2. (These equations describe the x and y

positions of a projectile that starts at the origin.) You should obtain an equation of the form y=ax+b x2where a and

b are constants.

10. Which projectile below has the greatest range and how much further does it travel than the other projectile?

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