Question

A ruler stands vertically against a wall. It is given a tiny impulse at such that it starts falling down under the influence of gravity. You can consider that the initial angular velocity is very small so that . The ruler has mass 250 g and length 30 cm. Use m/s for the gravitational acceleration, and the ruler has a uniform mass distribution. Note that there is no friction whatsoever in this problem. (See figure)

(a) What is the angular speed of the ruler when it is at an angle ? (in radians/sec)



unanswered

(b) What is the force exerted by the wall on the ruler when it is at an angle ? Express your answer as the x component and the y component (in Newton)



unanswered



unanswered

(c) At what angle will the falling ruler lose contact with the wall? ( ; in degrees) [hint: the ruler loses contact with the wall when the force exerted by the wall on the ruler vanishes.]

Answers

hell
omega= sqrt(2*g*(1-cos(theta)/L)
Mention in comments if answer is correct!
Anonymous
surely wrong !!!
hell
I meant
omega= sqrt((2*g)/L)*(1-cos(theta))
anonymous
omega= sqrt(3*g*(1-cos(theta))/L)
hell
and for friction both mg component and centripetal component is to be added??
Briggs
Any one know how to do b and c??
WLewin
Hello 801x-ers!

I would like to give you a little clue to solve the problem. When we say "the ruler loses contact with the wall when the force exerted by the wall on the ruler vanishes" means that Fx equals zero.

Good luck.

fima
apply conservation of energy:
U=m*g*hcm
EK= 1/2*I*w^2, I=1/3*m*L^2

Eini= mg(L/2) + 0
Efin= mg(L/2)cos30 + 1/2*I*w^2
solve for Eini=Efin -> w=

any one knows how to aswer the other questions?
Anonymous
who has the answer for b & c?
juanpro
could yo set numbers pleASE
socorro
please the number solutions?

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