Speed and velocity Knowledge-Based Practice

Questions

1. 1.

   At a particular instant, an object has a horizontal velocity component of 6.0 m/s and a vertical velocity component of -8.0 m/s. What is the instantaneous speed of the object at this instant?

   • A) 10 m/s
   • B) 14 m/s
   • C) 2.0 m/s
   • D) -2.0 m/s
2. 2.

   Which of the following combinations of speed and velocity is physically impossible for any moving object?

   • A) Constant speed and changing velocity
   • B) Changing speed and constant velocity
   • C) Changing speed and changing velocity
   • D) Constant speed and constant velocity
3. 3.

   Two objects, X and Y, move along a straight coordinate line with velocities of $+15\text{ m/s}$ and $-20\text{ m/s}$, respectively. Which of the following statements correctly compares their speeds and directions of motion?

   • A) Object Y has a greater speed than Object X, and they are moving in opposite directions.
   • B) Object X has a greater speed than Object Y, and they are moving in opposite directions.
   • C) Object X has a greater speed than Object Y, and they are moving in the same direction.
   • D) Object Y has a greater speed than Object X, and they are moving in the same direction.
4. 4.

   An object travels in two successive stages at constant speeds $v_1$ and $v_2$. Under which of the following conditions is the average speed for the entire motion equal to the arithmetic mean of the two speeds, $\frac{v_1 + v_2}{2}$?

   • A) When the time spent traveling during each stage is equal
   • B) When the distance traveled during each stage is equal
   • C) When the object reverses its direction of motion between the two stages
   • D) When the total displacement over the two stages is equal to zero
5. 5.

   Under which of the following conditions is an object's instantaneous velocity equal to its average velocity at every instant throughout a time interval?

   • A) When the object moves with a constant, non-zero acceleration along a straight path
   • B) When the object moves with a constant velocity throughout the entire interval
   • C) When the object maintains a constant speed along an arbitrary curved path
   • D) When the object's displacement over the entire interval is equal to zero
6. 6.

   A particle moves along a circular path of radius $r$ and completes half of a revolution in a time interval $\Delta t$. What is the ratio of its average speed to the magnitude of its average velocity over this interval?

   • A) $\frac{\pi}{2}$
   • B) $\frac{2}{\pi}$
   • C) $\pi$
   • D) 1
7. 7.

   In a position-versus-time graph for one-dimensional motion, what physical quantity is represented by the slope of a straight line connecting two points on the curve?

   • A) The average acceleration over the time interval
   • B) The average speed over the time interval
   • C) The instantaneous velocity at the initial point
   • D) The average velocity over the time interval
8. 8.

   A car travels along a straight road at a constant speed of 72 km/h. How many seconds does it take for the car to cover a distance of 600 m?

   • A) 8.3 s
   • B) 15 s
   • C) 30 s
   • D) 45 s
9. 9.

   A particle moves along a straight path, traveling 120 m in 4.0 s, remaining at rest for 2.0 s, and then traveling an additional 60 m in the same direction in 4.0 s. What is the average speed of the particle over the entire 10 s interval?

   • A) 15 m/s
   • B) 20 m/s
   • C) 22.5 m/s
   • D) 18 m/s
10. 10.

    A toy car moves along a straight coordinate axis from an initial position of $x_i = -12\text{ m}$ to a final position of $x_f = +18\text{ m}$ in 6.0 s. What is the average velocity of the car during this time interval?

    • A) +1.0 m/s
    • B) −5.0 m/s
    • C) +5.0 m/s
    • D) +3.0 m/s
11. 11.

    An object moves during a time interval $\Delta t$. If its average velocity over this interval is zero, which of the following statements must be true?

    • A) The net displacement of the object over the time interval is zero.
    • B) The average speed of the object over the time interval must also be zero.
    • C) The object remained at rest throughout the entire time interval.
    • D) The object moved along a straight path without reversing its direction.
12. 12.

    A drone flies 30 m due north in 10 s and then immediately flies 40 m due east in 10 s. What is the magnitude of the drone's average velocity for the entire 20 s trip?

    • A) 3.5 m/s
    • B) 2.5 m/s
    • C) 5.0 m/s
    • D) 7.0 m/s
13. 13.

    A cart moves along a straight horizontal track with an established coordinate system. If the cart has a negative velocity, which of the following statements must be true?

    • A) The cart is slowing down.
    • B) The position of the cart is on the negative side of the origin.
    • C) The cart is moving in the direction defined as negative.
    • D) The speed of the cart is also negative.
14. 14.

    Which of the following statements correctly describes a fundamental distinction between speed and velocity?

    • A) Speed is measured in meters per second, while velocity is measured in meters per second squared.
    • B) Speed is a vector quantity that specifies direction, while velocity is a scalar quantity that has only magnitude.
    • C) Speed can have a negative value depending on the coordinate frame, while velocity is strictly non-negative.
    • D) Speed is defined in terms of the distance traveled per unit time, while velocity is defined in terms of displacement per unit time.
15. 15.

    Which of the following statements correctly describes the relationship between the instantaneous speed and the instantaneous velocity of an object at any instant?

    • A) Instantaneous speed can be negative if the object moves in the negative coordinate direction.
    • B) Instantaneous speed is strictly greater than the magnitude of instantaneous velocity along a curved trajectory.
    • C) Instantaneous speed is always equal to the magnitude of the instantaneous velocity.
    • D) Instantaneous speed is determined by the total displacement divided by the elapsed time.
16. 16.

    A car travels along a curved road while its speedometer steadily reads 50 km/h. Which of the following statements correctly describes the car's speed and velocity during this turn?

    • A) Its speed is constant, but its velocity is changing because its direction of motion changes.
    • B) Both its speed and its velocity are constant because the speedometer reading does not change.
    • C) Both its speed and its velocity are changing because travel along a curved path alters both quantities.
    • D) Its velocity is constant, but its speed is changing because the trajectory is not straight.
17. 17.

    Under which of the following conditions is the average speed of an object equal to the magnitude of its average velocity over a given time interval?

    • A) When the object moves along a curved path at a constant speed
    • B) When the object moves in a closed loop and returns to its initial position
    • C) When the object travels along a straight line and reverses its direction of motion
    • D) When the object travels along a straight line in a single, unchanging direction
18. 18.

    An athlete runs 80 m due east in 10 s and then walks 20 m due west in 10 s. What is the average velocity of the athlete for the entire 20 s motion?

    • A) 5 m/s due east
    • B) 3 m/s due east
    • C) 5 m/s due west
    • D) 3 m/s due west
19. 19.

    A delivery van travels 60 km along a straight highway at a constant speed of 30 km/h and then travels another 60 km in the same direction at a constant speed of 60 km/h. What is the average speed of the van for the entire trip?

    • A) 45 km/h
    • B) 50 km/h
    • C) 40 km/h
    • D) 36 km/h
20. 20.

    A toy car completes one full lap around a circular track of circumference 12 m in 6 s, ending at its starting point. What are the average speed and the magnitude of the average velocity of the car for this trip?

    • A) Average speed is 0 m/s, and average velocity is 2 m/s
    • B) Average speed is 2 m/s, and average velocity is 2 m/s
    • C) Average speed is 2 m/s, and average velocity is 0 m/s
    • D) Average speed is 0 m/s, and average velocity is 0 m/s

Answers and step-by-step solutions appear after you finish the test.