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Homework #1

•  End of chapter problems: – Chapter 1: 3, 18, 24, 39 – Chapter 2: 3, 10, 21, 47, 50, 51, 75, 80

•  Due Wednesday, September 14

Reading Assignment

•  Read Chapter 3 •  Quiz on Monday, September 12 •  Multiple choice questions

Acceleration Acceleration is the rate of change of velocity.

Acceleration Acceleration is a vector, although in one-dimensional motion we only need the sign.

The previous image shows positive acceleration; here is negative acceleration:

If an object is moving in the opposite direction as the acceleration, the object is…

A. Speeding up B. Slowing down C. Moving at a constant speed D. Moving at a constant velocity E. Not enough info to tell

Acceleration Answer: slowing down. This is deceleration.

Deceleration occurs when the acceleration is opposite in direction to the velocity.

When the object’s acceleration and velocity are in the same direction, the object is speeding up.

What is the acceleration if the velocity is constant?

9/7/11

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Acceleration There is a difference between negative acceleration and deceleration:

Negative acceleration is acceleration in the negative direction as defined by the coordinate system.

Deceleration occurs when the acceleration is opposite in direction to the velocity.

Acceleration

The instantaneous acceleration is the average acceleration, in the limit as the time interval becomes infinitesimally short.

Demonstration – Motion with Carts

•  Hand in the green sheet •  Keep the white sheet

What is the average acceleration for..

A.  a= 0.5 m/s2

B.  a = 1 m/s2 C.  a = 0 D.  a < 0

1.  0-30s? 2.  70-90s?