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Mathematics
Mathematics
Problem
When a thin washer has outer radius
R
R
R
, inner radius
r
r
r
(
R
>
r
)
(R>r)
(
R
>
r
)
, and thickness
d
x
dx
d
x
measured along the
x
x
x
-axis, which of the following gives the differential volume
d
V
dV
d
V
of the washer? a)
d
V
=
π
(
R
−
r
)
2
d
x
dV=\pi\bigl(R-r\bigr)^{2}\,dx
d
V
=
π
(
R
−
r
)
2
d
x
b)
d
V
=
2
π
(
R
2
−
r
2
)
d
x
dV=2\pi\bigl(R^{2}-r^{2}\bigr)\,dx
d
V
=
2
π
(
R
2
−
r
2
)
d
x
c)
d
V
=
π
(
R
2
−
r
2
)
d
x
dV=\pi\bigl(R^{2}-r^{2}\bigr)\,dx
d
V
=
π
(
R
2
−
r
2
)
d
x
d)
d
V
=
π
(
R
2
+
r
2
)
d
x
dV=\pi\bigl(R^{2}+r^{2}\bigr)\,dx
d
V
=
π
(
R
2
+
r
2
)
d
x
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