1. Nov 12, 2013

### LDC1972

1. The problem statement, all variables and given/known data

Find piston velocity and
Find angular velocity AB about A.

I apologise if the image is poor! If very bad I'll elaborate in writing the values....

2. Relevant equations

Draw a velocity vector diagram to solve the above.
Also use 2∏RPM / 60 to convert crank speed from 3000 rpm to 314.16 rad / s
And then Wr to get 31.416 metres per sec angular speed of point A
And for "angular velocity AB about A" used Wab = Vab / Length ab = 17.4 / 0.2 = 87 rad / s. (But book says answer should be 21.25??

3. The attempt at a solution

Attached below my 'sketch'. I did this to clarify as well:

This is a simple slider crank example from one of my own books; the book gives the answers but not the method.

The answers given by book are:

34 m/s piston velocity (and I get this right)

Basically I did this:

1/ Drew question schematic to scale
2/ Drew Vector Vao (90 degrees to AO)
3/ Drew Vector Vab (90 degrees to AB at piston)
4/ Convert crank rpm to rad/s and then calculate Voa ( Voa = crank rad/s x length 0.1m)
5/ Draw vectors using the angles calculated from above methods (Voa being 30 degrees on right hand side from horizontal)
(Vab being 65 degrees from left hand side horizontal.
6/ Once first vector drawn point A is know, so join next (Vab) to a, and finally measure ao (Vao) to find o, and then drew horizontally across to find b.
7/ Then do Wab = Vab / length ab = 17.4/0.2 = 87 rad/s

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 12, 2013

### LDC1972

It's OK guys - tutor took a look and I am right, the book is wrong!
Thanks though..