Kinematics One Dimension Part 1

 

Kinematics in 1 Dimension By completing this course, you will: 

Understand and describe constant velocity situations.



Understand and describe accelerated motion situations.



Use kinematics equations to solve motion problems.

 

Kinematics in 1-D Concept Map Previous content

Physics

New content Studies

Motion

Described by

Constant Velocity

Kinematic Equations

Constant  Acceleration

Utilizes

Math Skills 08 : 3/32

 

Motion Almost everything we witness in our everyday lives involves motion:  motion: 

 

Definition

Kinematics   the mathematical description of Kinematics  motion without any reference reference to the cause. The cause of this motion will be described later. later.  –

 

Vector Preview Although vectors will be fully explained in a later tutorial, a brief introduction is needed here: A vector is a quantity that has magnitude, size, and direction.

Ex: Velocity, displacement, acceleration

A scalar is a quantity that has only magnitude, size.

Ex: speed, distance, temperature, mass

 

Similarities: Velocity and Velocity and speed are similar terms. They are often used interch interchangeably angeably.. However, there is a slight difference:

Speed   Scalar →

Velocity   Vector →

Velocity Velocity includes  includes a direction with magnitude, speed is  is only a magnitude. and speed

 

Vector Question A car is traveling at a constant 60mi/hr in a circular path.

Does it have a constant speed?  Y  Yes es Does it have a constant velocity? No, , because is constantly changing direction. No That is part ofit what velocity describes.

 

Constant Velocity Imagine that a toy train is moving along the tracks at a constant and steady rate. rate. There is no slowing or speeding in its motion.

This motion represents a constant velocity.

 

Velocity Formula: The velocity of this train can be found with:

Distance covered, m

Velocity, m/s

v Typical metric units are listed, but others can be used.

d   

t Time elapsed, sec

 

Average Velocity: Sometimes the previous formula is written as:

v 

dtotal t total

The bar bar above the v means average. If an object moves with a constant velocity, the average velocity is the same value.

If an object changes its velocity, this formula may be more useful.

 

Constant Velocity Example: If sun light takes about 8 minutes to go from the sun to the earth, how far away from the sun is the earth? Hi n t:   light travels at 186,000 186,000 miles miles per per second! second!

Illustration not to scale

 

Constant Velocity Example: If sun light takes about 8 minutes to go from the sun to the earth, how far away from the sun is the earth? Hi n t:   light travels travels at a constant constant 186,000 186,000 miles per second! Rearrange

v

  

d t

formula for desired variable

dt v

mi   x  480sec d     186,000   se c     d  89 x10  miles 6

8.0 minx 60   se c  480sec 1min

 

Instantaneous Velocity Instantaneous velocity: The speed of an object at any particular instant.  instant. 

The average speed and instantaneous speed may not be the same!

A car that gradually speeds up more and more has an instantaneous speed that always changes.

 

Instantaneous or Average Speed? If the police monitor your speed with a radar gun, are they checking your instantaneous speed or your average speed?

speed.  They Instantaneous speed.  would be interested in noticing if you exceed the speed limit at any point in time.

 

Thought Question? Two bicyclists initially km apart. They travel towards toward s eachare other at 1020 km/hr. km/hr . A bee is buzzing between them going from one to the other back and fourth at a constant 30 km/hr km/hr.. What is the total distance the bee travels before it gets crushed as the bicycles meet in the middle?

 

Solution to Thought Question This solution can be very easy, or very difficult, depending on how you go about it.

Easy way way: : The bicy clistsfor will1 meet time. Since the beebicyclists is flying hour in at 1 30hours km/hr km/hr, , it covers a total distance of 30km.

 

Assignment Page 30 Problems # 3,4,5,9 Write work for all problems! problems! Show formulas, math work, units! Odd problem have answers in the back of thenumbered book.