Conceptual Questions

    1. At this instant, is the particle in FIGURE Q4.1 speeding up, slowing down, or traveling at constant speed?

      FIGURE Q4.1

      The figure illustrates a velocity vector and an acceleration vector of a particle.

    2. Is this particle curving to the right, curving to the left, or traveling straight?

    1. At this instant, is the particle in FIGURE Q4.2 speeding up, slowing down, or traveling at constant speed?

      FIGURE Q4.2

      The figure illustrates a velocity vector and an acceleration vector of a particle.

    2. Is this particle curving upward, curving downward, or traveling straight?

  3. Tarzan swings through the jungle by hanging from a vine.

    1. Immediately after stepping off a branch to swing over to another tree, is Tarzan’s acceleration a⃗ zero or not zero? If not zero, which way does it point? Explain.

    2. Answer the same question at the lowest point in Tarzan’s swing.

  4. A projectile is launched at an angle of 30°.

    1. Is there any point on the trajectory where v ⃗ and a⃗ are parallel to each other? If so, where?

    2. Is there any point where v ⃗ and a⃗ are perpendicular to each other? If so, where?

  5. For a projectile, which of the following quantities are constant during the flight: x, y, r, vx , vy , v, ax , ay ? Which of these quantities are zero throughout the flight?

  6. A cart that is rolling at constant velocity on a level table fires a ball straight up.

    1. When the ball comes back down, will it land in front of the launching tube, behind the launching tube, or directly in the tube? Explain.

    2. Will your answer change if the cart is accelerating in the forward direction? If so, how?

  7. A rock is thrown from a bridge at an angle 30° below horizontal. Immediately after the rock is released, is the magnitude of its acceleration greater than, less than, or equal to g? Explain.

  8. Anita is running to the right at 5 m/s in FIGURE Q4.8. Balls 1 and 2 are thrown toward her by friends standing on the ground. According to Anita, both balls are approaching her at 10 m/s. Which ball was thrown at a faster speed? Or were they thrown with the same speed? Explain.

    FIGURE Q4.8

    The figure illustrates two balls approaching a person running toward the right. A horizontal velocity vector arrow labeled 5 m per s from the person points to the right.

  9. An electromagnet on the ceiling of an airplane holds a steel ball. When a button is pushed, the magnet releases the ball. The experiment is first done while the plane is parked on the ground, and the point where the ball hits the floor is marked with an X. Then the experiment is repeated while the plane is flying level at a steady 500 mph. Does the ball land slightly in front of the X (toward the nose of the plane), on the X, or slightly behind the X (toward the tail of the plane)? Explain.

  10. Zack is driving past his house in FIGURE Q4.10. He wants to toss his physics book out the window and have it land in his driveway. If he lets go of the book exactly as he passes the end of the driveway, should he direct his throw outward and toward the front of the car (throw 1), straight outward (throw 2), or outward and toward the back of the car (throw 3)? Explain.

    FIGURE Q4.10

    The figure illustrates the top view of a car labeled Zack in front of a driveway. The driveway is perpendicular to the road on which the car is moving.

  11. In FIGURE Q4.11, Yvette and Zack are driving down the freeway side by side with their windows down. Zack wants to toss his physics book out the window and have it land in Yvette’s front seat. Ignoring air resistance, should he direct his throw outward and toward the front of the car (throw 1), straight outward (throw 2), or outward and toward the back of the car (throw 3)? Explain.

    FIGURE Q4.11

    The figure illustrates the top view of two cars labeled Yvette and Zack. Zack's car is vertically below Yvette's car.

  12. In uniform circular motion, which of the following quantities are constant: speed, instantaneous velocity, the tangential component of velocity, the radial component of acceleration, the tangential component of acceleration? Which of these quantities are zero throughout the motion?

  13. FIGURE Q4.13 shows three points on a steadily rotating wheel.

    1. Rank in order, from largest to smallest, the angular velocities ω1, ω2, and ω3 of these points. Explain.

    2. Rank in order, from largest to smallest, the speeds v1, v2, and v3 of these points. Explain.

    FIGURE Q4.13

    The figure illustrates a wheel steadily rotating in the counterclockwise direction. Three points labeled 1, 2, and 3 are marked on the wheel.

  14. FIGURE Q4.14 shows four rotating wheels. For each, determine the signs (+ or −) of ω and α.

    FIGURE Q4.14

    The figure illustrates four rotating wheels labeled ("a") to (d).

  15. FIGURE Q4.15 shows a pendulum at one end point of its arc.

    1. At this point, is ω positive, negative, or zero? Explain.

    2. At this point, is α positive, negative, or zero? Explain.

    FIGURE Q4.15

    The figure illustrates a pendulum suspended from a horizontal support.