Physics Lab 1

Graph Matching

Eleanor Roosevelt High School

Chin-Sung Lin

Kinematics

Kinematics is a branch of mechanics. It is the science of describing the motion of objects using words, diagrams, numbers, graphs, and equations.

The goal of kinematics is to develop models to describe the motion of real-world objects.

Distance & Displacement

Scalars & Vectors

Scalars are quantities that are fully described by a magnitude (or numerical value) alone.

Vectors are quantities that are fully described by both a magnitude and a direction.

Distance & Displacement

Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion.

Displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.

Distance:10 m

Displacement:10 m East

10 m

Distance & Displacement

Distance/Position

t

d

Distance/Position

t

d

Distance/Position

t

d

Speed & Velocity

Speed

A speed (v) is a scalar quantity

Distance (d) covered per unit of time (t). Speed is a measure of how fast something is moving. It is the rate at which distance is covered

v = d / tUnit: meters per second (m/s), miles per hour

(mi/h), kilometers per hour (km/h)

Velocity

A velocity (v) is a vector quantity

Velocity is the measurement of the rate and direction of change in the displacement (d) of an object

v = d / tThe speed is the magnitude of velocity

Unit: meters per second (m/s), miles per hour (mi/h), kilometers per hour (km/h)

Speed & Velocity

Speed has only magnitude

Velocity has magnitude and direction

Speed/Velocity

t

v

Speed/Velocity

t

v

Speed/Velocity

t

v

Speed/Velocity

Speed: the slope of the distance-time (d-t) graph

t

d

slope = v (speed)

Acceleration

Acceleration

An acceleration (a) is a vector quantity

acceleration is the rate of change of velocity with time

a = Δv / t

a = acceleration (m/s2)

v = change of velocity (m/s)

t = time interval (s)

Acceleration

An acceleration (a) is also a scalar quantity

When linear (straight-line) motion is considered, it is common to use speed and velocity interchangeably and the acceleration may be expressed as the rate at which speed changes

a = Δv / t

a = acceleration (m/s2)

v = change of speed (m/s)

t = time interval (s)

Acceleration

t

a

Acceleration

t

a

Acceleration

Acceleration: the slope of the speed-time (v-t) graph

t

v

slope = ax (acceleration)

Distance, Speed & Acceleration

d-t

t

v

slope = ax

t

a

slope = 0

ax

t

d slope = increasing at constant rate

v-t a-t

The End