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Given:
The blade of this hacksaw is
mounted in a frame with a horizontal guide.
If
the motor turns the flywheel at a constant
CCW Speed of 60 RPM, find the acceleration
(linear) for the position when
θ
= 90
o
.
Problem Type:
Find:
Given:
Rigid Body Kinematics
ϖ
ΟΒ
= 60 RPM,
α
=0
Acceleration of the blade
First Step?
What do I know in this equation?
What do we know here?
Does the sign of the cross product make sense?
( 29
B
A
AB
B
A
AB
AB
B
A
r
r
a
a
/
/
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
×
+
×
×
+
=
α
ϖ
Can find r
A/B
(see triangle).
We will talk about how to
find
ϖ
AB
next time – for now
we are going to assume it is given as 1.432 rad/sec clockwise.
How can we find a
B
?
We have to do another acceleration equation relating B and O
.
Let’s do it.
( 29
O
B
OB
O
B
OB
OB
B
r
r
a
a
/
/
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
×
+
×
×
+
=
ϖ
= 6 0
RPM = 6.283 rad/sec and
α
= 0
Yes, the only component is the normal acceleration; B is moving in a circular path, so it’s acceleration
should be in the Y direction.
Equate the j’s
Reflection:
The acceleration of the hacksaw is always in the x direction.
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This note was uploaded on 01/22/2011 for the course ME 212 taught by Professor Staff during the Spring '05 term at Cal Poly.
 Spring '05
 staff

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