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# m2 statics watch

1. god! this is so confusing!
P135 M2 Edexcel

6 A uniform rod AB of length 4m and mass 4 kg is freely hinged at A to a vertical wall. A force P is applied at B at right anles to the rod in order to keep the rod in equilibirum at an angle of 30 degrees to the horizontal, as shown

Find a) the magnitude of P
b) the magnitude of R, the reaction of the hinge.

hm i think ive done the first bit right;
2(4g)(cos 30) = 4P
P = 17.0 N which is what thye get

but then b) is a total mind****.

thanks for any help
2. you have to use both moments and newtons 1st law.
3. (Original post by elpaw)
you have to use both moments and newtons 1st law.
1st?! You mean 3rd right?
4. (Original post by Nylex)
1st?! You mean 3rd right?
no, 1st. i.e. all the forces will be balanced if there is an equilibrium
5. (Original post by elpaw)
no, 1st. i.e. all the forces will be balanced if there is an equilibrium
Argh ok.
6. (Original post by elpaw)
you have to use both moments and newtons 1st law.
yup i got that far, it was more the calculating momentst that got me.
7. (Original post by kikzen)
god! this is so confusing!
P135 M2 Edexcel

6 A uniform rod AB of length 4m and mass 4 kg is freely hinged at A to a vertical wall. A force P is applied at B at right anles to the rod in order to keep the rod in equilibirum at an angle of 30 degrees to the horizontal, as shown

Find a) the magnitude of P
b) the magnitude of R, the reaction of the hinge.

hm i think ive done the first bit right;
2(4g)(cos 30) = 4P
P = 17.0 N which is what thye get

but then b) is a total mind****.

thanks for any help
ok for b), if you have the reaction force as R_h (horizontal component) and R_v (vertical component)

R_h = Psin30 = 8.5N

R_v = Pcos30 - 4g = -24.47N

|R| = sqrt(R_h² + R_v²) = 25.91 N
8. Take vertical and horizontal components and solve trigonometric simultaneous equations? Draw a force diagram?

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