Question

1. what is true about a car with constant velocity?

a. it has a positive acceleration c. it has a negative acceleration
b. it has zero acceleration d. it has a changing direction
part 2 fill in the blank: fill in the correct words to complete each statement. (1 pt per blank)

1. the velocity of an object must include both a and a.
2. a car slowing down as it is approaching a red traffic light has a acceleration;

when the light turns green, the cars acceleration is.
part 3 short answer: answer the following questions. for the math problems, make sure to show all work and circle/box your answer so that it stands out. double check all units!! point values indicated next to each question.

1. explain the difference, in relation to speed, between positive and negative acceleration. sketch and label a graph of each. be sure to label your axes!! (4 pts)

Explanation:

• Question 30: Velocity is a vector quantity. Constant velocity means no change in speed and direction. Acceleration is the rate of change of velocity. If velocity is constant (no change), acceleration \(a=\frac{\Delta v}{\Delta t}=0\) (where \(\Delta v = v_{final}-v_{initial}=0\)).
• Question 31: Velocity is a vector. By definition, a vector has both magnitude (how fast) and direction (which way).
• Question 32: When a car slows down, its velocity is decreasing. If we take the direction of motion as positive, then \(a=\frac{v_{final}-v_{initial}}{t}\) (\(v_{final}v_{initial}\), so \(a=\frac{v_{final}-v_{initial}}{t}>0\) (positive acceleration).

Answer:

• 30. B. it has zero acceleration
• 31. magnitude; direction
• 32. negative; positive