Velocity & Acceleration

• Mechanics - the study of the motion of objects. we focus on the language, principles, and laws that describe and explain the motion of objects

• Kinematics is the science of describing the motion of objects using words, diagrams, numbers, graphs, and equations.

• Kinematics is a branch of mechanics. The goal of any study of kinematics is to

develop sophisticated mental models that serve to describe (and ultimately, explain) the motion of real-world objects.

• Avoid memorizing the information; and avoid abstracting the information from the physical world that it describes and explains.

• Rather, contemplate the information, thinking about its meaning and its applications.

• your efforts should center on internalizing the meaning of the information.

• We will investigate the words used to describe the motion of objects.

• scalars, vectors, distance, displacement, • speed, velocity and acceleration. • These words are used with regularity to

describe the motion of objects. Your goal should be to become very familiar with their meaning.

Vector or Scalar

Scalar: a quantity that has only magnitude Vector : a quantity that has both

magnitude and directionScalar

Length, area, volumeSpeed

Mass, density

VectorDisplacement

Velocityacceleration

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.

• 5 m • 30 m/sec, East • 5 mi., North • 20 degrees Celsius • 256 bytes • 4000 Calories

• Scalar• Vector • Vector • Scalar• Scalar• Scalar

Speed and Velocity

Speed =

Distance

TimeVelocity=

Displacement

Time

A jogger has jogged 400. meters in 75 seconds. What is the jogger’s average speed?Speed = Distance/TimeSpeed = 400. m/75 secondsSpeed = 5.3 m/s

Example 1

Displacement and Distance

Distance: how much ground an object has covered during its motion.

Displacement: the object's overall change in position.

A plane is traveling north with a velocity of 502 m/s. How long will it take to travel 3200 meters?Velocity = Displacement/TimeTime = Displacement/VelocityTime = 3200 m /502 m/sTime = 6.4s

Example 2

Discuss and write in complete sentences

Why do we use velocity and displacement together or speed and distance together?

Compare and contrast

velocity and displacement are vectors speed and distance are scalars

What is the resulting displacement and distance of travel?

The diagram shows several of coach's positions at various times.

At each marked position, the coach makes a "U-turn" and moves in the opposite direction.

In other words, the coach moves from position A to B to C to D.

• 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.