(3) Estimate the torque you apply to open the classroomdoor (Hints: How long doe

Question

(3) Estimate the torque you apply to open the classroomdoor (Hints: How long does

(4) A 50kg woman is in a rotor with a 2m radius, layingagainst the inner surface. The

friction between the woman's sweater and the surfaceis s = 0:5. (a) Therotor

begins spinning with a constant angularacceleration
, and when the rotorreaches

enough angular speed, the oor drops but the woman stayssticking to the wall. (a)

What is the minimum angular velocity that will allow thewoman not to fall down

when the oor drops? (b) What's the maximum angularacceleration that will not

make the woman slide along the wall when the rotor isspeeding up to the angular

velocitycalculated in (a)?

Explanation / Answer

--------------- the door is around 2 meter width, and 80kg. so its moment of inertia is 80*2^2/3. the time taken is around 3 sec for /2 rad . so is around /9(rad/s2). F*2=/9 *80*4/3. so F=20N -------------------- We have that. for the woman to not be fall off. mg=N*=m^2r. so g=^2r =sqrt(r/g)=0,32(rad/s). --------------- the maximum acceleration. a*m=mg* where a=*r. so r=g so =g/r=2,45(rad/s2)

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