chapter two motion in one dimension 2.1 displacement 2.2 velocity 2.3 acceleration 2.4 motion...
TRANSCRIPT
Chapter TwoMotion in One Dimension
2.1 Displacement2.2 Velocity2.3 Acceleration2.4 Motion Diagrams2.5 One-Dimensional Motion with constant acceleration2.6 Freely Falling Objects
Observation What is it?How do we describe it?How does it happen?
Dynamics
• The branch of physics involving the motion of an object and the relationship between that motion and other physics concepts:
• Kinematics is a part of dynamics– In kinematics, you are interested in the description of motion
– Not concerned with the cause of the motion
How do we describe motion?So …..
Remember the Fundamental Quantities for Everything:
Length Mass Time (direction)
Motion should be able to be described with these quantities. HOW?
Quantities in Motion
• Any motion involves hierarchical concepts– Displacement in time– Velocity (change of the above)– Acceleration (change of the above)
• These concepts can be used to study objects in motion
The study of motion in time
The premeditated study of motion by the ancients was focused on the heavenly bodies.
The GREEKS were the first to study the heavens in a systematic and detailed manner. They understood the motion of the heavenly bodies. They created a model that explained the observations: GEOCENTRIC model
Copernicus corrected the understanding of motion: HELIOCENTRIC model
GALILEO really got things going.
Galileo Galilei (1564-1642)
Galileo’s workshopat the
Deutches Museumin
Munich, Germany
Galileo Galilei (1564-1642)
Made astronomical observations with a telescope
Experimental evidence for description of motion
Quantitative study of motion
Acceleration of gravity is independent of the mass of the falling object!
Iron ball
Wood ball
Galileo
Quantities in Motion
–Displacement in time– Velocity (change of the above)– Acceleration (change of the above
Defined as the change in position
Position
• Defined in terms of a frame of reference– A choice of coordinate axes – Defines a starting point for measuring
the motion• Or any other quantity
– One dimensional, so generally the x- or y-axis
In this chapter we are examining 1 dimensional motion
Displacement
• the change in position = –
• f stands for final and i stands for initial
– Units are meters (m) in SI
Δ ≡ −f ix x xΔ ≡ −f ix x x
NOTE: Displacement is DIFFERENT from length
Displacement REQUIRES a coordinate system
Displacement Examples
• From A to B– xi = 30 m– xf = 52 m Δx = 22 m– The displacement is
positive, indicating the motion was in the positive x direction
• From C to F– xi = 38 m– xf = -53 m Δx = -91 m– The displacement is
negative, indicating the motion was in the negative x direction
Displacement, Graphical
Quantities in Motion
– Displacement in time
– Speed & Velocity (change of the above)– Acceleration (change of the above
change in displacement in time
Scalar and Vector Quantities
• Scalar quantities are completely described by magnitude only
• Vector quantities need both magnitude (size) and direction to completely describe them– Generally denoted by boldfaced type and an
arrow over the letter– + or – sign is sufficient for this chapter