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P112 Spring 2007
Homework #2
Due: Friday Feb 2, 2007 – At lecture
Reading: 3.13.3, 3.5
Not all concepts will be covered in class – you are responsible
for all material in the reading and in the homework problems.
Warmup Exercises:
(Answer only will be marked)
1.
A car moving with constant acceleration covers the
distance between two points 70.0 m apart in 7.00 s. Its
speed as it passes the second point is 15.0m/s. What is
its speed at the first point, and what is its
acceleration?
2.
The manual of my car states that the stopping
distance is 50 m when the brakes are fully applied at
96 km/h. What is the deceleration? What is the
stopping time?
Mathematics Exercises:
3a.
Find the magnitude of vector
A
=4.00
i
+ 3.00
j
and
of vector
B
=5.00
i
2.00
j
. Write an expression for the
vector difference
AB
using unit vectors.
b)
What is the magnitude and direction of the vector
difference
AB
? Show
A, B
, and
AB
in a vector
diagram, and show that your diagram agrees
qualitatively with your answers from a).
c)
Find the scalar product of the vectors
A
and
B
.
What is the angle between the two vectors?
4a.
An object’s velocity is measured to be
v
x
(t) =
α

β
t
2
, where
α
=4.00 m/s and
β
=2.00 m/s
3
. At
t=0 the object is at x=0. Calculate the object’s
position and acceleration as functions of time.
b
) What is the object’s maximum positive
displacement from the origin?
c)
Draw graphs showing the object's position x(t),
velocity v
x
(t), and acceleration a
x
(t) as functions of
time t until the time in (b). Please align your graphs
one above another with their time axes synchronized.
Estimation:
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 Spring '07
 LECLAIR,A
 mechanics, Work

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