What is elapsed time?

The time interval between an event's start and end: $\Delta t = t_f - t_0$. Its SI unit is the second.

How is average velocity calculated?

Divide displacement by elapsed time: $\bar{v} = \Delta x/\Delta t$. Average velocity is a vector, so it includes direction.

What is the difference between distance and displacement?

Distance is total path length. Displacement is the change from initial to final position and includes direction.

What does instantaneous velocity mean?

An object's velocity at a specific instant, describing its motion over an extremely small time interval.

What does the slope of a position–time graph represent?

Velocity; the slope's sign indicates direction, and its steepness indicates velocity magnitude.

General physicsLesson 3 of 8 in the course Kinematics

Elapsed Time, Velocity, Speed, and Motion Graphs

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces elapsed time and velocity, which describe how position changes during motion. These ideas help answer questions such as how quickly an object moves and in which direction.

In physics, time is measured by comparing a change with a standard. The SI unit of time is the second, abbreviated $\text{s}$ . A clock or stopwatch lets us record when an event begins and ends.

All flashcards

What is elapsed time?: The time interval between an event's start and end: $\Delta t = t_f - t_0$ . Its SI unit is the second.
How is average velocity calculated?: Divide displacement by elapsed time: $\bar{v} = \Delta x/\Delta t$ . Average velocity is a vector, so it includes direction.
What is the difference between distance and displacement?: Distance is total path length. Displacement is the change from initial to final position and includes direction.
What does instantaneous velocity mean?: An object's velocity at a specific instant, describing its motion over an extremely small time interval.
What does the slope of a position–time graph represent?: Velocity; the slope's sign indicates direction, and its steepness indicates velocity magnitude.

Quiz questions

A person travels a total of $6\,\text{km}$ on a round trip and returns to the starting point in $0.5\,\text{h}$ . What is the average velocity?Answer: $0\,\text{km/h}$ , because the displacement is zero.
What does a car's speedometer report at a particular moment?Answer: Instantaneous speed, without the direction of motion.
What does the signed area between a velocity–time graph and the time axis represent over an interval?Answer: The object's displacement during that interval.
A horizontal segment of a velocity–time graph lies below the time axis. What does it indicate?Answer: Constant velocity in the negative direction.
A runner travels $400\,\text{m}$ in $80\,\text{s}$ . What is the runner's average speed?Answer: $5\,\text{m/s}$ .

Based on College Physics 2e by Paul Peter Urone, Roger Hinrichs (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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