Conceptual Questions

ssm Solution is in the Student Solutions Manual

| 1 | The speedometer of your car shows that you are traveling at a constant speed of 35 m/s. Is it possible that your car is accelerating? If so, explain how this could happen.

| 2 | Consider two people, one on the earth’s surface at the equator and the other at the north pole. Which has the larger centripetal acceleration? Explain.

| 3 | The equations of kinematics (Equations 3.3a 3.4a 3.5a 3.6b) describe the motion of an object that has a constant acceleration. These equations cannot be applied to uniform circular motion. Why not?

| 4 | Is it possible for an object to have an acceleration when the velocity of the object is constant? When the speed of the object is constant? In each case, give your reasoning.

| 5 | A car is traveling at a constant speed along the road ABCDE shown in the drawing. Sections AB and DE are straight. Rank the accelerations in each of the four sections according to magnitude, listing the smallest first. Justify your ranking.

| 6 | Other things being equal, would it be easier to drive at high speed around an unbanked horizontal curve on the moon than to drive around the same curve on the earth? Explain.

| 7 | ssm A bug lands on a windshield wiper. Explain why the bug is more likely to be dislodged when the wipers are turned on at the high rather than the low setting.

| 8 | What is the chance of a light car safely rounding an unbanked curve on an icy road as compared to that of a heavy car: worse, the same, or better? Assume that both cars have the same speed and are equipped with identical tires. Account for your answer.

| 9 | ssm A container is filled with water and attached to a rope. Holding the free end of the rope, you whirl the container around in a horizontal circle at a constant speed. There is a hole in the container, so that as you whirl it, water continually leaks out. Explain what, if anything, you feel as the water leaks out.

| 10 | A propeller, operating under test conditions, is being made to rotate at ever faster speeds. Explain what is likely to happen, and why, when the maximum rated speed of the propeller is exceeded.

| 11 | A penny is placed on a rotating turntable. Where on the turntable does the penny require the largest centripetal force to remain in place? Give your reasoning.

| 12 | Explain why a real airplane must bank as it flies in a circle, but a model airplane on a guideline can fly in a circle without banking.

| 13 | ssm Would a change in the earth’s mass affect (a) the banking of airplanes as they turn, (b) the banking of roadbeds, (c) the speeds with which satellites are put into circular orbits, and (d) the performance of the loop-the-loop motorcycle stunt? In each case, give your reasoning.

| 14 | A stone is tied to a string and whirled around in a circle at a constant speed. Is the string more likely to break when the circle is horizontal or when it is vertical? Account for your answer, assuming the constant speed is the same in each case.

| 15 | A fighter plane is diving toward the earth. At the last instant, the pilot pulls out of the dive on a vertical circle and begins climbing upward. In such maneuvers, the pilot can black out if too much blood drains from his head. Why does blood drain from his head?

| 16 | Go to Concept Simulation 5.2 at to review the concepts involved in this question. Two cars are identical, except for the type of tread design on their tires. The cars are driven at the same speed and enter the same unbanked horizontal turn. Car A cannot negotiate the turn, but car B can. Which tread design yields a larger coefficient of static friction between the tires and the road? Give your reasoning in terms of centripetal force.

Copyright © 2007 John Wiley & Sons, Inc. All rights reserved.