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Chapter 2. Uniformly Accelerated Motion. Speed. Velocity. Acceleration. What are the units for acceleration?. Uniformly Accelerated Motion Along a Straight Line. In this case… acceleration is a constant
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Chapter 2 Uniformly Accelerated Motion
Acceleration What are the units for acceleration?
Uniformly Accelerated Motion Along a Straight Line • In this case… • acceleration is a constant • and the acceleration vector lies in the line of the displacement vector.
The 5 Equations! (1) (2) (3) (4) (5)
Problem Solution Guidelines • Draw a sketch • Indicate origin and positive direction • List the given quantities using the symbols of the equations. (si, vi, a) • Is time known or do we need to find it? • What are we to solve for? • Write the general equations of kinematics
More Guidelines • Rewrite the general equations using the known quantities. • Look at the knowns and unknowns and map a strategy of solution. • Check your units • Make sure you are answering the question.
Problem Solution Time • Fifteen minutes
Definitions • Instantaneous Velocity • the slope of the displacement versus time graph • Instantaneous Acceleration • the slope of the velocity versus time graph
A B Slopes Displacement Time
Teaming Exercise Next Problem solutions
Free Fall • The force of gravity points downward • Acceleration of gravity near the surface of Earth is called g = 9.8 m/s2 = 32.1 ft/s2 • Air resistance ignored • We have then the conditions of one-dimensional kinematics – straight line motion with constant acceleration.
Sample Problem • A ball is thrown vertically upward at 10 m/s. How high will it get, how long will it be in the air, and how fast will it be moving when it hits the ground.
Projectile Problems – Two Dimensional Kinematics • Ignore air resistance. • ax = 0 • ay = g = 9.81 m/s2 downward
The motions in the two directions are independent Horizontal Vertical
2-D Problem Guidelines • Set up two 1-D solutions Origin x Origin y Positive x Positive y xi = yi = vxi = vyi = ax = 0 ay = g
2-D Guidelines Cont’d • Write general kinematic equations for each direction • Rewrite them for the problem at hand • Find the condition that couples the motions (usually time)