Physics Chapter 2: Kinematics

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Questions and Answers

What distinguishes a vector from a scalar quantity?

Vectors include both magnitude and direction. (correct)

Vectors have a magnitude only.

Scalars represent a change in position.

Scalars can have direction associated with them.

If a person runs 5 laps around a 200m track, what is their distance traveled?

400m

1000m

2000m (correct)

What is the displacement if the initial position is 10m and the final position is 3m?

7m right

7m left

10m

-7m (correct)

Which statement about distance and displacement is true?

Displacement can be negative depending on position. Signup and view all the answers

Which of the following is NOT true about average speed?

It represents the net change in position. Signup and view all the answers

What is instantaneous velocity?

The speed of an object at a specific moment. Signup and view all the answers

If an object returns to its starting position, what is its displacement?

Zero. Signup and view all the answers

When is displacement less than distance traveled?

When the object changes direction while moving. Signup and view all the answers

What is the key difference between speed and velocity?

Velocity has direction, while speed does not. Signup and view all the answers

How is average speed calculated?

Total distance divided by time taken. Signup and view all the answers

Which of the following statements regarding distance and displacement is true?

Distance has magnitude only, while displacement has both magnitude and direction. Signup and view all the answers

What happens to the instantaneous acceleration as the duration of time approaches zero?

It approaches the average acceleration. Signup and view all the answers

Which of the following represents a scalar quantity?

Speed Signup and view all the answers

If Megan walks 1100m to the left in 330 s, what is her average speed?

$3.3 m/s$ Signup and view all the answers

What is the SI unit of velocity?

meters per second Signup and view all the answers

Which of the following best describes a scalar quantity?

A quantity that has only magnitude Signup and view all the answers

What is the primary difference between average speed and average velocity?

Average speed is calculated using total distance, while average velocity uses displacement. Signup and view all the answers

If a car is moving around a circular track with constant speed, what can be said about its velocity?

The instantaneous velocity changes direction continuously. Signup and view all the answers

Which of the following statements correctly differentiates distance from displacement?

Displacement can be negative, indicating direction. Signup and view all the answers

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

Instantaneous velocity of the object Signup and view all the answers

In a velocity-time graph, what does a horizontal line indicate?

Constant velocity Signup and view all the answers

How can you determine an object's average velocity from a graph?

By calculating the slope of the position-time graph. Signup and view all the answers

What does a negative value for average velocity signify?

The object is moving backward relative to the reference point. Signup and view all the answers

Study Notes

Chapter 2: Kinematics

Kinematics is the study of motion without considering the cause.
It describes how things move.
For example, the heart moving blood through veins while you rest is an example of kinematics.

Warm-up Session

The father of the scientific method is Galileo Galilei.

Significant Figures

The number of significant figures in 0.005 is 1.

Vectors vs Scalars

Scalars have only magnitude.
Vectors have both magnitude and direction.
Vectors are represented by arrows.
Vectors can be one-dimensional.

Displacement

Position tells us where an object is at a particular time.
Distance is a scalar that represents the total distance traveled.
Displacement is a vector that represents the net change in position.
- If you run 4 laps around a 400m track, your distance is 1600m, but your displacement is 0m.
Displacement is the difference between the final and initial positions.
Δx = xf - xo
- Δx is displacement
- xf is the final position
- xo is the initial position
If direction changes during movement, displacement is less than distance traveled.
A professor pacing left and right across a 3.5 m wide whiteboard will have a displacement of +2 m to the right depending on initial position.

Displacement Calculation Example

If initial position is 2m and final position is 4.5m to the right, the displacement is 2.5 m.

Distance

Distance is the magnitude of displacements between two positions.
It's the total length of the path traveled between two positions.
Distance has no direction.

Speed and Velocity

Speed is a scalar, calculated as total distance divided by time.
- Speed = distance / time
Velocity is a vector that has magnitude and direction.
- Average velocity = displacement / elapsed time
- Δx / Δt = (xf - xo) / (tf - to)

Time, Velocity, and Speed

The SI unit for time is the second (s).
The SI unit for speed and velocity is meters per second (m/s), or kilometers per hour (km/h).
Velocity is a vector quantity, while speed is a scalar quantity.

Average Speed Example

Megan walks 1100m to the left in 330 s. Her average speed is 3.3 m/s.

Instantaneous Velocity

Instantaneous velocity is the average velocity over an infinitesimally short time interval.
v = lim (Δx / Δt) as Δt approaches 0

Acceleration

Acceleration is the rate of change of velocity.
a = Δv / Δt
The SI unit for acceleration is meters per second squared (m/s²).
Acceleration is a vector quantity.
Instantaneous acceleration is acceleration at a specific moment in time.
Deceleration is acceleration opposite to direction of motion.

Acceleration Examples

A car accelerates from rest to 20 m/s in 10 seconds has an acceleration of 2 m/s².
A car decelerates from 30 m/s to rest in 10 seconds has an acceleration of -3 m/s².
A truck accelerating from 15m/s to 45m/s in 5 seconds has an acceleration of 6 m/s².

Kinematic Equations for Constant Acceleration

Several equations allow for solving motion problems. Note them down correctly:
- ā = (ν-νο) / t
- v = vo + at
- x = xo + vot + 1/2 at²
- v² = vo² + 2a( x− xo)

Freely Falling Objects

A freely falling object moves only under the influence of gravity.
Acceleration due to gravity (g) is approximately 9.80 m/s².
The kinematic equations apply to freely falling objects.

Dropping/Throwing a Ball Example Problems

Problems involving a ball dropped or thrown upward from a height, which involve finding time to hit the ground or final velocity/maximum height.

Graphical Representation

Plots of physical quantities against each other allow us to determine velocity and acceleration.
The slope of a position-time graph gives velocity.
The slope of a velocity-time graph gives acceleration.
The area under a velocity-time graph gives displacement.

Problem Solving Skills

Steps for solving physics problems:
- Read the problem carefully. Identify objects, questions, and applicable laws/principles.
- Draw a diagram showing coordinates.
- Identify given & inferred quantities. Determine quantities to find.
- Select equations for solving the desired unknowns.
- Solve symbolically (using variables).
- Keep track of significant figures while calculating values.
- Ensure appropriate accuracy in the final answer.
- Check the reasonableness of the solution—does it make sense, considering known physical constants and the question?
- Keep careful track of units.

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Description

Explore the fundamentals of kinematics, the study of motion. This quiz covers key concepts such as vectors vs. scalars, significant figures, and displacement. Test your understanding of how objects move and the principles governing their motion.