0 5 10 15 20 25 30 0 2 4 6 Time (s) X (m) 8

P211 Final Sample 1
7) A block A of mass m A lies on a horizontal table in contact with a block B of mass m B . An
external force F is applied to block B, as shown on the figure below, such that both blocks are
sliding to the left. A coefficient of kinetic friction μ k is present between either block and the table.
What is the acceleration of block A?
Block A
mass m A
Block B
mass m B
Force F
μ k
A)
F
m A
B)
F − μ
km
m
A
A
g
C)
F − μ
km
Bg
m
B
D)
F − μ
km
Ag
m + m
A
B
E)
F − μ
k
(m
A
+ m
m + m
A
B
B
)g
8) As the figure shows, a 4.4 kg block is accelerated by a compressed spring whose spring constant
is 320 N/m. After leaving the spring at the spring's relaxed length, the block travels over a horizontal
surface, with a coefficient of kinetic friction of μ k = 0.25, for a distance of 7.8 m before stopping.
Through what distance was the spring compressed before the block began to move?
A) 0.184 m B) 0.361 m C) 0.512 m
D) 0.725 m E) Insufficient information has been provided
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