Mechanics question

13

A uniform pole AB, of mass 30 kg and length 3 m, is smoothly hinged to a vertical wall at one end A. The pole is held in equilibrium in a horizontal position by a light rod CD. One end C of the rod is fixed to the wall vertically below A. The other end D is freely jointed to the pole so that ACD = 30 and AD = 0.5 m, as shown in Figure 3. Find

(a) the thrust in the rod CD, (The ?'s are angles in degrees)

I have got the answer as 340 N, can someone check this for me please.

And what does the terminology 'thrust' mean , I've never come across it in mechanics before.

This is M2 by the way.

Thanks in advance.

Reply 1

Kolya

17

What you've written isn't appearing correctly. "The other end D is freely jointed to the pole so that <WHAT?> and AD = 0.5m".

Reply 2

JohnnySPal

2

Thrust = "pushing force". I guess it's analagous to tension in string. The thrust pushes the pole AB upwards to maintain equilibrium.

Argh I last did M2 four years ago, I'm rusty. You're gonna have to cnsider moments to do this, I think. The system is in equilibrium so you'll possibly have

30g x 1.5 = Tcos30 x 0.5

So T = 1018N?

Bah I'm probably wrong. TBH I'm trying this more for fun than to actually help :p:

Reply 3

callum Honisett

OP

13

JohnnySPal

Thrust = "pushing force". I guess it's analagous to tension in string. The thrust pushes the pole AB upwards to maintain equilibrium.

Argh I last did M2 four years ago, I'm rusty. You're gonna have to cnsider moments to do this, I think. The system is in equilibrium so you'll possibly have

30g x 1.5 = Tcos30 x 0.5

So T = 1018N?

Bah I'm probably wrong. TBH I'm trying this more for fun than to actually help :p:

I tried resolving forces to get my answer, can you use this method here?

Mechanics question

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