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Learning Introductory Physics with Activities

Section 2.7 Modeling Motion

Exercises Practice Activities

Figure 2.7.1. A simple strobe diagram.

1. Warm-up.

Is the average speed of the upper object greater than, less than, or equal to the average speed of the lower object? Explain your reasoning.

2. The Ball in the Air.

Imagine throwing a ball straight into the air.
  1. Describe the motion in words (use complete sentences).
  2. Identify any quantities of interest by symbol.
  3. Draw a motion diagram for the ball.
  4. Discuss any assumptions or idealizations you want to make.
Estimate the average velocity of the ball:
  1. During the entire motion
  2. During the first half of the motion
  3. During the second half of the motion
Do you think it would be appropriate or necessary to use a calculator for this activity?

3. The Runaway Cart.

Determine the average velocity during each time interval for the cart in the figure below. How would you estimate the instantaneous velocity at t2? What acceleration can you estimate? Do you think it would be appropriate or necessary to use a calculator for this activity?
Figure 2.7.2. A simple strobe diagram.