Velocity at Piston P and angular velocity of link HP help

[bobmarly12345]

Homework Statement

The instantaneous configuration of a slider crank mechanism has a crank GH 10cm long, the connecting rod HP is 50cm. The crank makes an angle of 60 degree with the inner dead centre position and is rotating at 110 rev/min. Determine the velocity of the piston P and the angular velocity of the link HP.

cannot find any simliar examples in textbooks or online which will help me with this question.

Homework Equations

The Attempt at a Solution

Really have no idea where to start but I've made a start whether its right i don't know.

Right, first off I've converted the 110rev/min=w into 11.5Rads/s
so w=11.5Rads/s
i then assumed you had to find the velocity at H in order to find the velocity at P
so Velocity at H = (Wgh) X gh
Vh = 11.5rads/s X 0.1m
= 1.15ms^-1

(i don't know if that is correct for starters & how i use that to find the velocity at P then the angular velocity at HP, please help?)

 

[LCKurtz]

Before putting all the numbers in, I would label the length of the crankshaft $c$, and the radius of the wheel $r$, the distance $PG = x$. Then write an equation giving $x$ in terms of the angle of rotation $\theta$. Solve the equations you need before plugging in numbers.

 

[bobmarly12345]

i have an idea of what you mean but I'm still quite lost

 

[LCKurtz]

You are going to have to show some effort. Drop a perpendicular down from H to the horizontal axis. That breaks $x$ into two legs of right triangles. You should be able to use trigonometry and the Pythagorean theorem to express $x$ in terms of the angle of rotation $\theta$ and the other constants $r$ and $c$. Ultimately, the velocity of the piston will be $\frac{dx}{dt}$.

 

[bobmarly12345]

would this formula work, [ -rw(cos(60)+((sin2(60)/(2xsqrt(n²-sin²(60)))) ]
where n = L/R
i get a negative value when i use it, the piston is moving in the negative direction.

 

[LCKurtz]

I'm sorry, but since you don't seem to care about my suggestions, I am resigning from this problem.