• In this chapter we will only look at motion along a line (one dimension).

• Motion can be forward (positive displacement) or backwards (negative displacement)

Chapter 2: Motion in One Dimension-continued

Reading assignment: Chapter 3

Homework 3 (due Friday, Sept. 2, 2005, 10 pm):

(Chapter 3) Q4, 6, 11, 24, 39, 54

TUTOR & HOMEWORK SESSIONS This year’s tutors: Jerry Kielbasa, Matt Rave, Christine Carlisle

 

All sessions will be in room 103 (next to lecture room).  

 Tutor sessions in semesters past were very successful and received high marks from students.

All students are encouraged to take advantage of this opportunity. 

Monday Tuesday Wednesday Thursday Friday Saturday Sunday

4-6 Jerry 5-7

Christine

4-6 Jerry5-7 Matt

  3-5 Jerry

 

6-8 Christine

6-8 Matt

Review from Friday:

• Displacement x, velocity v, acceleration a

• a = dv/dt = d2x/dt2, and v = dx/dt.

• x is slope of v-graph, v is slope of a-graph.

One-dimensional motion with acceleration

atvv 0 * as function of time

)(2 02

02 xxavv Velocity as function of ______________

Derivations: Book pp. 44-46

200 2

1attvxx * as function of time

____________ as function of time and velocitytvvxx )( 02

10

Black board example 2.7 (see book)

Spotting a police car, you brake a Porsche from a speed of 100 km/h to speed 80 km/h during a displacement of 88.0 m at a constant acceleration.

(a) What is your acceleration?

(b) How long did it take to slow down?

Notice that acceleration and velocity often point in different directions!!!

Black board example 2.8

A car traveling at constant speed of 45.0 m/sec passes a trooper hidden behind a billboard. One second after the speeding car passes the billboard, the trooper sets out from the billboard to catch it, accelerating at a constant rate of 3.00 m/s2.

(a) How long does it take her to overtake the car?

(b) How far has she traveled?

Freely falling objects

In the absence of air resistance, all objects fall towards the earth with the same constant acceleration (a = -g = -9.8 m/s2), due to gravity

General Problem-Solving Strategy

Conceptualize __________________________________

Categorize__________________________________

Analyze __________________________________

Finalize __________________________________

Black board example 2.9

A stone thrown from the top of a building is given an initial velocity of 20.0 m/s straight upward. The building is 50 m high. Using tA = 0 as the time the stone leaves the throwers hand at position A, determine:

(a) The time at which the stone reaches its maximum height.

(b) The maximum height.

(c) The time at which the stone returns to the position from which it was thrown.

(d) The velocity of the stone at this instant

(e) The velocity and and position of the stone at t = 5.00 s.

Review:

• Displacement x, velocity v, acceleration a

• a = dv/dt = d2x/dt2, and v = dx/dt.

• Know x, v, a graphs. x is slope of v-graph, v is slope of a- graph.

• For constant acceleration problems (most problems, free fall):

• Equations on page 36-7 (const. Acceleration & free fall).

• Free fall

atvv 02

00 2

1attvxx