Unit 5.3 | ES II | Velocity vs Time Graphs

Choose the Velocity vs. Time Graph that best matches this Position vs. Time Graph

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Answer explanation

In a Position vs Time graph, the horizontal axis shows position. When the line is horizontal, the position is not changing, therefore, the velocity never increases from zero. That is why in the Velocity vs. Time graph, the red lines is directly on the x-axis.

Choose the Velocity vs. Time Graph that best matches this Position vs. Time Graph

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Answer explanation

The slope of a Position-Time graph represents velocity. The Position-Time graph showed a straight line with a positive slope. Because the slope is constant in the Position-Time Graph, the Velocity vs. Time graph shows a horizontal line (velocity not changing). The line is above the x-axis in the Velocity vs. Time graph because the velocity is positive.

Choose the Velocity vs. Time Graph that best matches this Position vs. Time Graph

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Answer explanation

The slope of a Position-Time graph represents velocity. The Position-Time graph showed a straight line with a negative slope. Because the slope is constant in the Position-Time Graph, the Velocity vs. Time graph shows a horizontal line (velocity not changing). The line is below the x-axis in the Velocity vs. Time graph because the velocity is negative.

Choose the Velocity vs. Time Graph that best matches this Position vs. Time Graph

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Answer explanation

The slope of a Position-Time graph represents velocity. The first portion of the Position-Time graph has a straight line with a negative slope. Therefore the Velocity-Time graph has a horizontal line (velocity not changing) below the x-axis (negative velocity).

The slope of the line then becomes positive, indicating a change in direction AND a change in the sign of the velocity. Therefore, in the Velocity vs. Time graph the line crosses the x-axis, and the velocity becomes positive.

Choose the Velocity vs. Time Graph that best matches this Position vs. Time Graph

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Answer explanation

The slope of a Position-Time graph represents velocity. The first portion of the Position-Time graph has a straight line with a positive slope. Therefore the Velocity-Time graph has a horizontal line (velocity not changing) above the x-axis (positive velocity).

The slope of the line then becomes negative, indicating a change in direction AND a change in the sign of the velocity. Therefore, in the Velocity vs. Time graph the line crosses the x-axis, and the velocity becomes negative.

Choose the Velocity vs. Time Graph that best matches this Position vs. Time Graph

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Answer explanation

The slope of a Position-Time graph represents velocity. The first portion of the Position-Time graph has a straight line with a positive slope. Therefore the Velocity-Time graph has a horizontal line (velocity not changing) above the x-axis (negative velocity).

The Position-Time graph then shows a straight line, indicating that the position is not changing anymore. This means that velocity is 0, therefore, on the Velocity vs. Time graph the line goes to the x-axis (v = 0 m/s).

During what times is the object at rest?

• 0 - 2 secs

• 2 - 4 seconds

• 4 - 8 seconds

Answer explanation

Between 0 and 2 seconds the velocity is 0 m/s (right on the x-axis). That indicates the object is stationary.

During what times is the object moving the fastest?

• 0 - 2 secs

• 2 - 4 seconds

• 4 - 8 seconds

Answer explanation

Between 0 - 2 seconds the velocity is 0 m/s.

Between 2 - 4 seconds the velocity is 2 m/s

Between 4 - 8 seconds the velocity is -1 m/s.

The object is moving fastest between 2-4 seconds.

Tags

NGSS.MS-PS3-1

During what times is the object moving in the negative direction?

• 0 - 2 secs

• 2 - 4 seconds

• 4 - 8 seconds

Answer explanation

Between 0 - 2 seconds the velocity is 0 m/s.

Between 2 - 4 seconds the velocity is 2 m/s

Between 4 - 8 seconds the velocity is -1 m/s.

The direction of the object is indicated by the sign of the velocity. Therefore, the object is moving in the negative direction between 4 - 8 seconds when the velocity is -1 m/s.

The following velocity-time graph shows Violet's motion over 4 seconds.  Which statement best describes her motion?

• 1. Violet moves forward slowly, then turns around and moves back quickly.

• 1. Violet moves forward quickly, then turns around and moves backward at the same speed.

• 1. Violet is at 1 m for 2 seconds, then runs quickly to -2 m and stands there for 2 seconds.

• 1. Violet is at 1 m for a while, then teleports to -2 m and stays there.

Answer explanation

1. Violet moves forward slowly, then turns around and moves back quickly.

From 0 - 2 seconds the velocity is 1 m/s. That means Violet is moving in the positive direction at a slow pace.

At 2 seconds the velocity graph passes over the x-axis which means the object changes direction.

From 2 - 4 seconds the velocity is -2 m/s. That means the speed of the object has increased and the object is travel in the opposite direction.

Tags

NGSS.MS-PS3-1