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Ch 02: Kinematics in One Dimension
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 2, Problem 6a

A particle starts from at and moves with the velocity graph shown in FIGURE EX2.6. Does this particle have a turning point? If so, at what time?

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1
Step 1: Understand the concept of a turning point. A turning point occurs when the velocity of the particle changes direction, i.e., when the velocity becomes zero and then reverses its sign.
Step 2: Analyze the velocity graph provided. The graph shows the velocity of the particle as a function of time. The velocity starts at 0 m/s, increases to 20 m/s, remains constant, and then decreases back to 0 m/s before becoming negative.
Step 3: Identify the time at which the velocity becomes zero after being positive. From the graph, the velocity decreases linearly and reaches 0 m/s at t = 10 seconds.
Step 4: Check if the velocity becomes negative after t = 10 seconds. The graph shows that the velocity becomes negative after t = 10 seconds, indicating a change in direction.
Step 5: Conclude that the particle has a turning point at t = 10 seconds, as this is the time when the velocity transitions from positive to zero and then to negative.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Velocity and Turning Points

In physics, a turning point occurs when a particle changes its direction of motion. This is typically indicated by a change in the sign of the velocity. In a velocity-time graph, a turning point is where the velocity crosses the time axis, indicating that the particle has stopped and is about to move in the opposite direction.
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Velocity-Time Graph Interpretation

A velocity-time graph visually represents an object's velocity over time. The slope of the graph indicates acceleration, while the area under the curve represents displacement. In this case, the graph shows a constant velocity followed by a decrease, which suggests that the particle is moving at a steady speed before slowing down, potentially indicating a turning point.
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Constant Velocity

Constant velocity means that an object is moving at a uniform speed in a straight line, with no acceleration. In the provided graph, the particle maintains a velocity of 20 m/s for a period before decreasing. This constant velocity phase indicates that the particle is not experiencing any net forces acting on it, allowing it to move steadily until it begins to decelerate.
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