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Introductory mechanics
Chapter 03  Motion In Two Or Three Dimensions
Due at 11:59pm on Tuesday, September 23, 2008
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Position, Velocity, and Acceleration
Learning Goal:
To identify situations when position, velocity, and /or acceleration change, realizing that change can be in
direction or magnitude.
If an object's position is described by a function of time,
(measured from a nonaccelerating reference frame), then the
object's velocity is described by the time derivative of the position,
, and the object's acceleration is described by
the time derivative of the velocity,
.
It is often convenient to discuss the average of the latter two quantities between times
and
:
and
.
Part A
You throw a ball. Air resistance on the ball is negligible. Which of the following functions change with time as the ball flies
through the air?
Hint A.1
Newton's 2nd Law
Hint not displayed
ANSWER:
only the position of the ball
only the velocity of the ball
only the acceleration of the ball
the position and velocity of the ball
the position and the velocity and acceleration of the ball
Part B
You are driving a car at 65 mph. You are traveling north along a straight highway. What could you do to give the car a nonzero
acceleration?
Hint B.1
What constitutes a nonzero acceleration?
Hint not displayed
ANSWER:
Press the brake pedal.
Turn the steering wheel.
Either press the gas or the brake pedal.
Either press the gas or the brake pedal or turn the steering wheel.
Part C
A ball is lodged in a hole in the floor near the outside edge of a merrygoround that is turning at constant speed. Which
kinematic variable or variables change with time, assuming that the position is measured from an origin at the center of the
merrygoround?
Hint C.1
Change of a vector
Hint not displayed
ANSWER:
the position of the ball only
the velocity of the ball only
the acceleration of the ball only
both the position and velocity of the ball
the position and velocity and acceleration of the ball
Part D
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MasteringPhysics: Assignment Print View
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For the merrygoround problem, do the magnitudes of the position, velocity, and acceleration vectors change with time?
Hint D.1
Change of magnitude of a vector
Hint not displayed
ANSWER:
yes
no
An Object Accelerating on a Ramp
Learning Goal:
Understand that the acceleration vector is in the direction of the change of the velocity vector.
In one dimensional (straight line) motion, acceleration is accompanied by a change in speed, and the acceleration is always
parallel (or antiparallel) to the velocity.
When motion can occur in two dimensions (e.g. is confined to a tabletop but can lie anywhere in the xy plane), the definition of
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 Spring '10
 PICKETT
 Physics, Derivative, Acceleration, Velocity, Assignment Print View

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