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A car drives past point x=0 at time t=0 at a
constant speed of 50 km/hr. Shortly after it
accelerates rapidly to 100 km/hr at t1. It holds
this speed until a rabbit runs onto the road at t2
when the car comes to a screeching stop. Which
of the curves shown above best represents the
car’s i) velocity ii) acceleration?
A person pulls a block across a rough horizontal surface at a constant
speed by applying a force F. The arrows in the diagram below correctly
indicate the directions, but not necessarily the magnitudes of the
various forces on the block. Which of the following relations among
the force magnitudes must be true? 
v

F

fk

W
a ) F  f k and N  W
b) F  f k and N  W
c) F  f k and N  W
d ) F  f k and N  W

N
e) None of the above
In the figure on the right, a block of
slides down the roof, starting from rest.
To calculate the speed as it leaves the
roof, which is the best choice of axes?
y
x
(a) Because the horizontal direction is
always in the x-direction
x
(b) Because the force of gravity is
always in the y-direction
y
y
(c) Because the acceleration is along
the direction of the roof
(d) None of the above
Which of the following is the best FBD of m1?
(Assume the pulley is frictionless, the string
has negligible mass and the coefficient of
friction between the block and incline is  )
N
a)
T
f  N
N
c)
b)
T
f  N
W  m1 g
W  m1 g
N
a
d)
a
T
T
f  N
W  m1 g
f  N
m2
a
N
a
m1
W  m1 g

a
The FBD on the right is for a
block accelerating up an
inclined plane. Which are the
correct equations?
(a) Fy  ma y
N  W sin   ma
( b)  Fy  ma y  0
N  W cos  0
(c)  Fy  ma y  0
N  W cos  0
F
x
m
Wsinθ
y
Wcosθ
W= m g
f = μN
max
N
T1  W cos   f  ma
F
x
 ma x
T1  W sin   f  ma
F
x
T1
 ma x
T1  W sin   f  ma
x
