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m/s

A car enters the freeway with a speed of 6.4 m/s and accelerates uniformly for 3.2 km in 3.5 minutes. How fast (in m/s) is the car moving after this time? (units)

m

A car starts from rest and travels for 5.0 s with a constant acceleration of -1.5 m/s^2. How far does the car travel in this time interval? (units)

kinematics

branch of mechanics that explains the "what" and "how" of motion

Dynamics

A branch of physics that focuses on force and how they relate to motion.

mechanics

branch of applied mathematics dealing with motion and the forces producing motion

Displacement (delta X)

Vector drawn from the initial position to the final position

Meter (m)

SI unit Length

Direction of Displacement

Positive/negative depending on what direction it is pointing to

Magnitude of Displacement Vector

Shortest distance between the initial and final positions of the object

Displacement vs. Distance

Displacement is the shortest distance between two points, whereas distance is the path traveled by the object

Average Speed

Distance traveled divided by the time required to cover the distance

Average Speed Formula

Avg. Speed = Distance/Elapsed time

Meters per second

SI Unit for Average Velocity/Speed

Average Velocity

Dividing displacement by elapsed time

Average Velocity Formula

V= x (f) - x (i) / t(f) - t (i)

Direction of Average Velocity

Points in the same direction as displacement

Instantaneous Velocity

How fast an object is moving and direction of motion at each instant in time

Instantaneous Speed

Magnitude of instantaneous velocity

Average acceleration

a = ∆v/∆t

Average Acceleration Formula

a = v (f) - v (i) / t (f) - t (i)

SI Unit of Average Acceleration

Meter per second squared (m/s^2)

Direction of Average Acceleration Vector

In same direction as average velocity

Instantaneous acceleration

Average acceleration as change in time approaches 0

Whenever acceleration and velocity have opposite directions:

The object slows down and is said to be "decelerating"

Kinematic Equations for Constant Acceleration

(1) v (f) = v (i) + at

Rule for Using Kinematic Equations for Constant Acceleration

If three variables are known, the fourth variable can always be found

Problem Solving Insight for Kinematics

(1) Decide at start which directions are positive and which are negative

Free-Fall

Idealized motion in which air resistance is neglected and the acceleration is nearly constant

Acceleration due to gravity

9.8 m/s/s or m/s^2 in the metric system

Displacement in Free Fall

Use "y" instead of "x"

Always a downward-pointing vector

Direction of Acceleration Due to Gravity

Symmetry in Free-Fall Motion

(1) Time required for object to reach maximum heigh equals the time for it to return to its starting point