Chapter 3 Study Guide: Projectile Motion



Chapter 3 Study Guide: Projectile Motion

Multiple Choice

Identify the choice that best completes the statement or answers the question. Write the letter of your response on the line provided.

____ 1. A scalar is a quantity that has _____.

|a. |magnitude and time |c. |time a direction |

|b. |magnitude and direction |d. |only a magnitude |

____ 2. In order to find the components of a vector, you should _____.

|a. |draw the vector with the correct magnitude and orientation |

|b. |measure the sides of the right triangle |

|c. |draw a right triangle so that the vector is the hypotenuse |

|d. |all of the above |

____ 3. In the absence of air resistance, the angle at which a thrown ball will go the farthest is _____.

|a. |15° |c. |45° |

|b. |30° |d. |60° |

____ 4. A ball thrown in the air will never go as far as physics ideally would predict because _____.

|a. |the ball would never land |c. |air resistance slows the ball |

|b. |gravity is acting on it |d. |all of the above |

____ 5. A cannonball is launched from the ground at 30 m/s at an angle of 30° above the horizontal. Ignoring air resistance, the ball with hit the ground with a speed of _____.

|a. |0 m/s |c. |30 m/s |

|b. |20 m/s |d. |9.8 m/s2 |

____ 6. A projectile launched horizontally hits the ground in 0.8 seconds. If it had been launched with twice the speed in the same direction, it would have hit the ground in _____.

|a. |less than 0.8 s |

|b. |twice the amount of time |

|c. |more than 0.8 s |

|d. |0.8 s |

____ 7. An object is dropped and falls freely to the ground with an acceleration of g. If it thrown upward at an angle instead, its acceleration would be _____

|a. |less than g |c. |g |

|b. |more than g |d. |zero |

____ 8. Which best approximates the resultant of a pair of 6-unit vectors perpendicular to each other?

|a. |0 units |c. |8 units |

|b. |6 units |d. |12 units |

____ 9. Which best approximates the resultant of a pair of 6-unit vectors parallel to each other?

|a. |0 units |c. |8 units |

|b. |6 units |d. |12 units |

____ 10. What is the resultant of a 3-unit vector and a 4-unit vector at right angles to each other?

|a. |1 units |c. |7 units |

|b. |5 units |d. |none of the above |

____ 11. When in orbit, a satellite such as the Hubble telescope or the moon is _____.

|a. |simply a projectile |c. |free from Earth’s gravity |

|b. |not acceleration |d. |moving with constant velocity |

____ 12. Suppose a small plane can fly at 170 km/h and that there is a tailwind of 60 km/h. How fast does the plane’s shadow move across the ground?

|a. |110 km/h |c. |185 km/h |

|b. |170 km/h |d. |230 km/h |

____ 13. Ignoring air resistance, at what other angle will a thrown ball go the same distance as one thrown at an angle of 75°?

|a. |15° |c. |80° |

|b. |65° |d. |90° |

____ 14. Ignoring air resistance, at what other angle will a thrown ball go the same distance as one thrown at an angle of 10°?

|a. |15° |c. |80° |

|b. |65° |d. |90° |

____ 15. When calculating the resultant of two vectors pointed in opposite directions, _____.

|a. |the magnitudes should be added |c. |the magnitudes should be multiplied |

|b. |the magnitudes should be subtracted |d. |use the Pythagorean theorem |

True/False

Indicate whether the statement is true or false. Write the letter of your response on the line provided.

____ 16. The vector sum is called the resultant.

____ 17. When adding two vectors at right angles, the resultant of the vectors is the algebraic sum of the two vectors.

____ 18. A ball will go farthest when thrown at a 45° angle.

____ 19. Any vector can be represented by two other vectors that are at right angles to each other.

____ 20. Time is an example of a vector quantity.

Numeric Response

Respond to each of the following problems in the space provided. Make sure your numerical responses include both a number and a unit.

21. A motorboat is driven across a river at 3.0 km/h at a right angle to the current, which is flowing at 10 km/h. Sketch a diagram of this problem labeling each vector, then calculate the resultant vector.

22. An airplane heads north at a speed of 230 km/h with a crosswind blowing from the west at 80 km/h. Sketch a diagram of this problem labeling each vector, then calculate the resultant vector.

Problem

An airplane flies at 295 km/h parallel to the direction of the wind. The wind speed is 40 km/h. What are the two possible speeds of the plane relative to the ground? Explain your answer.

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