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Given: The punch is operated by a simple
harmonic motion of the pivoted section.
The motion is
measured to be
θ
=
θ
o
sin 2
π
t.
Find the acceleration of
the punch when t = 10 seconds if
θ
o
=
π
/12.
Set up acceleration equation(s).
Let’s label some points on
the punch (A and B).
List the acceleration equation for B.
What do I know in this equation?
Now back to the a
B
equation.
Problem Type:
Find:
Given:
Rigid Body Kinematics (doesn’t ask
about forces)
θ
=
θ
ο
sin
2π
t
Acceleration of the punch
First Step?
What do we know here?
Reflection:
This is more simple than the general case because
θ
was equal to
zero.
We could have found the
θ , ϖ ,
and
α
as a function of time and plotted out
the accelerations as a function of time. If we knew the mass of the punch, we
could also determine the forces on the pin at B.
Does the sign of the cross product make
sense?
A
B
( 29
A
B
AB
A
B
AB
AB
A
B
r
r
a
a
/
/
2
2
2
2
2
2
2
×
+
×
×
+
=
α
ϖ
Really only r
B/A
.
We will talk about how to
find
ϖ
AB
next time – for now we are
going to assume it is given as 2.3 rad/sec clockwise.
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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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