Section 2.1 Displacement and Velocity

Which of the following situations represents a positive displacement of a carton? Assume positive position is measured vertically upward along a y-axis.

• A delivery person waiting for an elevator lowers a carton onto a dolly.

• When the elevator doors open, the delivery person lifts the dolly over the threshold of the elevator.

• The delivery person pushes the dolly to the back of the elevator while pressing a floor button.

• The door closes and the elevator moves from the 10th to the 4th floors.

Refer to the figure above to answer questions 2–4.

_____ 2. What is the correct description of any change of position farther to the right of zero?

• positive displacement

• positive distance

• positive position

• positive change of displacement

A dog walks from +4 m to +2 m. Which of the following statements is true about the dog’s motion?

• x_i = +2 m     

• 
  

   $\Delta$   x = +2 m

•  x_f = +2 m  

• v_avg = 2 m/s

What is the maximum negative displacement a dog could have if it started its motion at +3 m?

• +7 m

• +3 m

• -3 m

• -7 m

Rank in decreasing order the displacements of objects having the following pairs of average velocity and time of motion.
 I. vavg = +2.0 m/s,  $\Delta$  t = 2.0 s
II. vavg = +3.0 m/s,  $\Delta$  t = 2.0 s
III. vavg = -3.0 m/s,  $\Delta$  t = 3.0 s                   

• I, II, III  

• II, III, I 

•  II, I, III

• III, II, I

Rank in decreasing order the distances traveled by objects having the following pairs of average velocity and time of motion.
I. vavg = +2.0 m/s,  $\Delta$  t = 2.0 s
II. vavg = +3.0 m/s,  $\Delta$  t = 2.0 s
III. vavg = -3.0 m/s,  $\Delta$  t = 3.0 s

• I, II, III  

• II, III, I  

• II, I, III

• III, II, I

The graph above shows the motion of a dog pacing along a fence. Refer to the graph to answer questions 7-10.

_____ 7. For the five time intervals shown, during how many intervals does the dog have the same average velocity?

• 0

• 1

• 2

• 3

The graph above shows the motion of a dog pacing along a fence. Refer to the graph to answer questions 7-10.

For the five time intervals shown, during how many intervals does the

dog pace at the same average speed?

• 0

• 1

• 2

• 3

Describe the dog’s motion when it is at 1.0 m.

Calculate: What is the dog’s average velocity for total displacement?