Kinematics: Motion Descriptors and Relative Motion

Practice flashcards covering kinematics concepts: motion definitions, motion descriptors (time, distance, displacement, speed, velocity, acceleration), and basic problem examples from the lecture notes.

What is kinematics?

The study of the motion of points, objects, and systems without considering the causes of motion.

From which Greek word is 'kinematics' derived and what does it mean?

Derived from 'kinema', meaning movement.

Name the six motion descriptors studied in this lecture.

Time, Distance, Displacement, Speed, Velocity, Acceleration.

What two quantities are required to describe motion?

Position and time.

How is motion defined in the notes?

The change of position of an object in a specific span of time relative to an observer.

What is displacement?

The length and direction of the straight line from the object's initial position to its final position.

What is distance?

The total length traveled by an object; a scalar quantity.

How do speed and velocity differ in terms of quantity type?

Speed is a scalar; velocity is a vector (has magnitude and direction).

What is the SI unit for speed and velocity?

Meters per second (m/s).

What is acceleration?

The rate of change of velocity with respect to time; a vector quantity with units m/s^2.

Name the three indications that an object is accelerating.

Change in magnitude of velocity, change in direction of motion, or both.

What do positive and negative acceleration mean?

Positive acceleration speeds up; negative acceleration (deceleration) slows down.

Is motion absolute or relative?

Motion is relative to the observer; different observers may see motion differently.

How is velocity defined with respect to a reference point?

Velocity is the rate of change in position with respect to a reference point and includes direction.

How is average speed computed in the example 'Bryle runs 600 m in 10 s'?

Average speed = distance/time = 600 m / 10 s = 60 m/s.

Given vi=25 m/s, vf=40 m/s, t=6 s, what is acceleration?

a = (vf − vi)/t = (40 − 25)/6 = 2.5 m/s^2.

Given vi=25 m/s, vf=40 m/s, t=6 s, what is average velocity?

Average velocity = (vi + vf)/2 = 32.5 m/s.

A bike starts from rest with a = 5 m/s^2 and travels 1020 inches. What is velocity after travel?

Convert 1020 inches to meters (≈25.9 m); v = sqrt(2as) ≈ sqrt(2·5·25.9) ≈ 16.1 m/s.

A 3 m jump height requires what takeoff speed (neglect air resistance)?

Takeoff speed v0 = sqrt(2 g h) ≈ sqrt(2·9.8·3) ≈ 7.7 m/s.

If distance is 305 km in 5 h, what is the average speed?

Average speed = distance/time = 305 km / 5 h = 61 km/h.

If traveling at the same average speed, how far can you travel in 8 hours at 61 km/h?

Distance = 61 km/h × 8 h = 488 km.

How long would it take to travel 483 km at an average speed of 61 km/h?

Time = distance / speed = 483 km / 61 km/h ≈ 7.93 h.

Is distance always greater than, equal to, or less than displacement?

Distance is always greater than or equal to displacement.

Is displacement a scalar or vector quantity? And distance?

Displacement is a vector; distance is a scalar.

What quantity describes when an event took place?

Time.

What is the SI unit of time?

Seconds (s).

How would you describe acceleration in terms of velocity and time?

Acceleration is the rate of change of velocity with respect to time; it is a vector.