posted by keitanako on .
A ruler stands vertically against a wall. It is given a tiny impulse at Î¸=0âˆ˜ such that it starts falling down under the influence of gravity. You can consider that the initial angular velocity is very small so that Ï‰(Î¸=0âˆ˜)=0. The ruler has mass m= 100 g and length l= 35 cm. Use g=10 m/s2 for the gravitational acceleration, and the ruler has a uniform mass distribution. Note that there is no friction whatsoever in this problem. (See figure)
(b) What is the force exerted by the wall on the ruler when it is at an angle Î¸=30âˆ˜? Express your answer as the x component Fx and the y component Fy (in Newton)
(c) At what angle Î¸0 will the falling ruler lose contact with the wall? (0â‰¤Î¸0â‰¤90âˆ˜; in degrees) [hint: the ruler loses contact with the wall when the force exerted by the wall on the ruler vanishes.]
Eini= mg(L/2) + 0
Efin= mg(L/2)cos30 + 1/2*I*w^2
ax = -L/2*sin(theta) w^2 + L/2*cos(theta) alpha