# Algebra-Based Physics I (PHY 2053) Chapter 2 Physics Homework For Mastering

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University of North Florida

**Algebra-Based Physics I (PHY 2053)**

Position versus Time Graphs Conceptual Question

The motions described in each of the questions take place at an intersection on a two-lane road with a stop sign in each direction. For each motion, select the correct position versus time graph. For all of the motions, the stop sign is at the position , and east is the positive x direction.

Part A

A driver ignores the stop sign and continues driving east at constant speed. Hint 1. Determining velocity from a position versus time graph The slope on a position versus time graph is the rise (change in position) over the run (change in time). In physics, the ratio of change in position over change in time is defined as the velocity. Thus, the slope on a position versus time graph is the velocity of the object being graphed.

Hint 2. Driving east

Since east is defined as the positive x direction, a car traveling east must have a positive velocity. A positive velocity is represented

as a positive slope on a position versus time graph.

Hint 3. Constant speed

Since velocity is represented by the slope on a position versus time graph, a car moving at constant speed must be represented by

a line of constant slope.

Part B

A driver ignores the stop sign and continues driving west at constant speed.

Hint 1. Determining velocity from a position versus time graph The slope on a position versus time graph is the rise (change in position) over the run (change in time). In physics, the ratio of change in position over change in time is defined as the velocity. Thus, the slope on a position versus time graph is the velocity of the object being graphed.

Hint 2. Driving west

Since east is defined as the positive x direction, a car traveling west must have a negative velocity. A negative velocity is represented as a negative slope on a position versus time graph.

Hint 3. Constant speed

Since velocity is represented by the slope on a position versus time graph, a car moving at constant speed must be represented by a line of constant slope.

Part C

A driver, traveling west, slows and stops at the stop sign.

Hint 1. Determining velocity from a position versus time graph The slope on a position versus time graph is the rise (change in position) over the run (change in time). In physics, the ratio of change in position over change in time is defined as the velocity. Thus, the slope on a position versus time graph is the velocity of the object being graphed.

Hint 2. Driving west

Since east is defined as the positive x direction, a car traveling west must have a negative velocity. A negative velocity is represented as a negative slope on a position versus time graph.

Hint 3. Acceleration

Since velocity is represented by the slope on a position versus time graph, a car that accelerates must be represented as a curve with changing slope. If a car slows, then the slope of the graph must approach zero. If a car’s speed increases, the slope must become more positive or more negative (depending upon which direction it is moving).

Part D

A driver, after stopping at the stop sign, travels east with a positive acceleration.

Hint 1. Determining velocity from a position versus time graph The slope on a position versus time graph is the rise (change in position) over the run (change in time). In physics, the ratio of change in position over change in time is defined as the velocity. Thus, the slope on a position versus time graph is the velocity of the object being graphed.

Hint 2. Driving east

Since east is defined as the positive x direction, a car traveling east must have a positive velocity. A positive velocity is represented as a positive slope on a position versus time graph.

Hint 3. Acceleration

Since velocity is represented by the slope on a position versus time graph, a car that accelerates must be represented as a curve with changing slope. If a car slows, then the slope of the graph must approach zero. If a car’s speed increases, the slope must become more positive or more negative (depending upon which direction it is moving)

Part A

Consulting the graph shown in the figure, find the object’s average velocity over the time interval from 0 to 1 second.

Answer to the nearest integer.

Hint 1. Definition of average velocity Average velocity is defined as the constant velocity at which an object would have to travel to achieve a given displacement (difference between final and initial positions, which can be negative) over a given time interval, from the initial time to the final

time . The average velocity is therefore equal to the displacement divided by the given time interval. In symbolic form, average velocity is given by

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