Lesson Plan

Period #4 Velocity Review / Intro To Acceleration

Materials : Textbook : Physics - Principles and Problems

Velocity Fun Sheet

Lab #3 - Measuring Acceleration

Review : Go over Questions 13-18 on pages 55 of textbook

Practice finding average and instantaneous velocity, find displacement using a velocity vs time graph, and review terms and definitions, practice calculations using velocity formula

Objectives : students should be able to :

 

Kinematics (Acceleration in One Dimension)

It is expected that students will demonstrate an understanding of the relationships between time, velocity, displacement, and acceleration and apply these relationships to calculations in common situations.

    1. define acceleration
    2. use velocity-versus-time graphs to determine the instantaneous or average acceleration of objects
    3. solve problems for objects with constant acceleration, involving: displacement , initial velocity, final velocity, acceleration, time

 

Part I - Acceleration - Introduction and Notes :

Give Notes starting at "ACCELERATION" p. 2-23, define acceleration, and introduce the formula for acceleration.

Do examples on pages 2-23 and 2-24

Do Lab #3 - Measuring Acceleration

Guided Study :

"Check your understanding" page 2 -25, find acceleration in both cases.

Exercise :

Questions 1-4 page 66 Practice Problems in Textbook

Questions 9 - 12 page 69 Practice Problems in Textbook

Evaluation :

Lab #3 - Measuring Acceleration

Questions 1-4 page 66 Practice Problems in Textbook

Acceleration Quiz

Unit Two Test

 

Displacement During Acceleration

Practice Questions :

  1. A skier accelerates from rest at 1.20 m/s2 down an icy slope. How far does she get in a) 5.0 s? b) 10.0 s c) 15.0 s?

    2.  

  2. What is the acceleration of an object that accelerates steadily from rest, traveling 2.0 m/s in 2.0 s?

    3.  

  3. How long does it take an airplane accelerating from rest at 5.0 m/s2 to travel 360 m?

 

Ans.

  1. 15 m, 60.0 m, 135 m
  2. 1.0 m/s
  3. 12 s
  4. Displacement and Acceleration : 2-26

We can calculate the displacement of an object that has CONSTANT acceleration.

We know that

vave = vf + vi

2

so since

d = vave t = (vf + vi) t

2

We also know that :

aave = vf - vi

t

we can solve this equation for vf

vf = at + vi

and substitue this equation into our first equation

d = (at + vi + vi) t = (2vi + at) t = vit + ½ at2

2 2

d = vit + ½ at2

** remember, this equation holds true ONLY at constant acceleration

note what happens when velocity is constant (ie. a = 0)

d = vit + ½ at2

zero

and out equation becomes

d = vt (since if v is constant vi = vf = vave)

In the SPECIAL CASE of Acceleration From Rest vi = 0

and the equation becomes :

d = vit + ½ at2 = ½ at2

zero

Example

A. How far down a smooth ramp does a 5.0 kg cart roll in 8.0 seconds accelerating from rest at 2.5 m/s?

d = ½ at2 = ½ (2.5 m/s)(8.0 s)2 = 8.0 x 101 m

B. How far will it roll if its initial velocity was 2.0 m/s?

d = vit + ½ at2 = (2.0 m/s)(8.0s) + ½ (2.5 m/s)(8.0 s)2

= 96 m