Critical Thinking
Applying Concepts A girl moves at 2 m/s delivering newspapers. She throws a newspaper directly behind her at 2 m/s. In the frame of reference of someone standing nearby, what is the motion of the newspaper?
Designing an Experiment Design an experiment to measure the speed of a toy train going around a circular track.
Analyzing Data A raft floats downstream. After 1 minute it has moved 50.0 meters. After 2 minutes it has moved 100.0 meters. After 3 minutes it has moved 150.0 meters. Could the raft's speed be constant? Explain.
Problem Solving A rocket ship is moving through space at 1000 m/s. It accelerates in the same direction at 4 m/s2. What is its speed after 100 seconds?
Math Skills
Use the following graph to answer Questions 29 and 30.
Using Graphs The graph above shows the motion for a person walking down a street. Describe the history of the motion.
- Using Graphs How fast is the person walking during the first 10 seconds?
Calculating A car starts from rest and increases its speed to 15 m/s in 20 seconds. What is the car's acceleration?
Concepts in Action
Predicting The propulsion system of the rocket ship described in problem 28 is tested. Its rockets are fired and the ship accelerates from rest at 5 m/s2 for 2 minutes. How does the ship's final velocity compare with the ship's initial velocity in problem 28?
Comparing and Contrasting Compare the case of a rubber ball falling through the air and a rubber ball bouncing up and down on a hard floor. For which of these cases is the instantaneous acceleration always the same as the constant acceleration?
Calculating Two trains on parallel tracks are traveling in the same direction. One train starts 10 km behind the other. It overtakes the first train in 2 hours. What is the relative speed of the second train with respect to the first train?
Writing in Science Write a paragraph explaining how different reference frames affect descriptions of motion in the following scenario. A basketball player dribbles down the court at a constant speed and then shoots the ball into the basket. Describe the motion of the ball from the reference frame of a camera mounted directly behind the basket. Then, describe the motion of the ball from the reference frame of the basketball player. (Hint: Sketch displacement versus time graphs of the ball's motion based on each reference frame.)
Performance-Based Assessment
Creating a Table Use a table to present the distances and displacements between familiar places. In a third column include the average speed at which you travel between these places. Be sure to list the places in pairs, such as home and school, a park and the library, or your bed and front door. Estimate the displacement if you can't measure it.
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