Physics Problem Set Solutions
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Questions and Answers

If the velocity of a particle is nonzero, can its acceleration be zero? Explain.

Yes. If the velocity of the particle is nonzero, the particle is in motion. If the acceleration is zero, the velocity of the particle is unchanging, or is a constant.

If the velocity of a particle is zero, can its acceleration be nonzero? Explain.

Yes. If you drop a doughnut from rest (v = 0), then its acceleration is not zero. A common misconception is that immediately after the doughnut is released, both the velocity and acceleration are zero. If the acceleration were zero, then the velocity would not change, leaving the doughnut floating at rest in mid-air.

Two cars are moving in the same direction in parallel lanes along a highway. At some instant, the velocity of car A exceeds the velocity of car B. This means that the acceleration of A is greater than that of B.

False

Secretariat won the Kentucky Derby with times for successive quarter-mile segments of 25.2 s, 24.0 s, 23.8 s, and 23.0. Find his average speed during each quarter-mile segment.

<p>The average speed during the first quarter mile segment is 52.4 ft/s (35.6 mi/h). The average speed during the second quarter mile segment is 55.0 ft/s (37.4 mi/h). For the third quarter mile of the race, the average speed is 55.5 ft/s (37.7 mi/h), and during the final quarter mile, the average speed is 57.4 ft/s (39.0 mi/h).</p> Signup and view all the answers

Assuming that Secretariat's instantaneous speed at the finish line was the same as the average speed during the final quarter mile, find his average acceleration for the entire race. (Horses in the Derby start from rest.)

<p>Assuming that Secretariat's final velocity is 57.4 ft/s, and his initial velocity is 0 ft/s, his average acceleration during the race is 0.598 ft/s².</p> Signup and view all the answers

Draw motion diagrams for the following: (a) an object moving to the right at a constant speed, (b) an object moving to the right and speeding up at a constant rate (c) an object moving to the right and slowing down at a constant rate, (d) an object moving to the left and speeding up at a constant rate, and (e) an object moving to the left and slowing down at a constant rate.

<p>(a) An object moving to the right at a constant speed = Motion diagram showing arrows of equal length, all pointing to the right. (b) An object moving to the right and speeding up at a constant rate = Motion diagram showing arrows pointing to the right, with increasing length. (c) An object moving to the right and slowing down at a constant rate = Motion diagram showing arrows pointing to the right, with decreasing length. (d) An object moving to the left and speeding up at a constant rate = Motion diagram showing arrows pointing to the left, with increasing length. (e) An object moving to the left and slowing down at a constant rate = Motion diagram showing arrows pointing to the left, with decreasing length.</p> Signup and view all the answers

How would your drawings change if the changes in speed were not uniform, that is, if the speed were not changing at a constant rate?

<p>The spacing of the successive positions in the motion diagrams would change with less regularity. The object would move with some combination of the kinds of motion shown. Within one drawing, the acceleration vectors would vary in magnitude and direction.</p> Signup and view all the answers

The position versus time for a certain particle moving along the x-axis is shown. Find the average velocity in the time intervals: (a) 0 to 2s, (b) 0 to 4s, (c) 2 s to 4 s, (d) 4 s to 7s, (e) 0 to 8 s.

<p>(a) 5 m/s, (b) 1.2 m/s, (c) -2.5 m/s, (d) -3.3 m/s, (e) 0 m/s</p> Signup and view all the answers

A person walks first at a constant speed of 5.00 m/s along a straight line from point A to point B and then back along the line from B to A at a constant speed of 3.00 m/s. What is (a) her average speed over the entire trip? (b) her average velocity over the entire trip?

<p>(a) 3.75 m/s (b) 0</p> Signup and view all the answers

The position of a particle moving along the x-axis varies in time according to the expression x = 3t², where x is in meters and t is in seconds. Evaluate its position (a) at t = 3.00 s and (b) at 3.00 s + Δt. (c) Evaluate the limit of Δx/Δt as Δt approaches zero, to find the velocity at t = 3.00 s.

<p>(a) 27.0 m, (b) 27.0 m + (18.0 m/s)Δt + (3.00 m/s²)(Δt)², (c) 18.0 m/s</p> Signup and view all the answers

A particle moves along the x-axis according to the equation x = 2.00 + 3.00t - 1.00t², where x is in meters and t is in seconds. At t = 3.00 s, find (a) the position of the particle, (b) its velocity, and (c) its acceleration.

<p>(a) 2.00 m, (b) -3.00 m/s, (c) -2.00 m/s²</p> Signup and view all the answers

Study Notes

Answers to Problem Sets

  • Problem 7: If a particle's velocity is non-zero, its acceleration can be zero. A constant velocity means unchanging velocity, thus zero acceleration.

  • Problem 8: If a particle's velocity is zero, its acceleration can be non-zero. An object dropped from rest accelerates due to gravity.

  • Problem 9: A car exceeding another car's velocity doesn't necessarily mean it has a larger acceleration. Cars can have the same or different accelerations, or the second car may have recently accelerated more.

  • Problem 13 (a): Secretariat's average speeds for each quarter mile segment are: first - 35.6 mi/h, second - 37.4 mi/h, third - 37.7 mi/h, final - 39.0 mi/h.

  • Problem 13 (b): Secretariat's average acceleration during the race was 0.598 ft/s².

  • Problem 18: Motion diagrams for various scenarios of constant and non-uniform acceleration. (diagrams described, but not included in the summary)

  • Problem 3: Average velocities for given time intervals.

    • 0 to 2s: 5 m/s
    • 0 to 4 s: 1.2 m/s
    • 2 to 4 s: -2.5 m/s
    • 4 to 7 s: -3.3 m/s
    • 0 to 8 s: 0 m/s
  • Problem 5 (a): Average speed during the entire trip was 3.75 m/s.

  • Problem 5 (b): Average velocity over the entire trip is 0 m/s because the walker starts and finishes at the same place.

  • Problem 6:

    • Position at 3 seconds was 27 meters.

    • Position at 3.00s+𝞰t was 27.0m +(18.0m/s)𝞰t+(3.00m/s²)𝞰t²

    • Velocity at 3.00 seconds was 18 m/s.

  • Problem 15 (a): The particle's position at t = 3.00 seconds is 2.00 meters.

  • Problem 15 (b): The particle's velocity at t = 3.00 seconds is -3.00 m/s.

  • Problem 15 (c): The particle's acceleration is -2.00 m/s².

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Description

This quiz focuses on solving various problems related to motion, acceleration, and velocity in physics. It covers different scenarios including constant and non-uniform acceleration, as well as examples like Secretariat's speed during a race. Test your understanding of these concepts with this comprehensive problem set.

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