You have been asked to be a stunt consultant for a motion picture about a geneti

Question

You have been asked to be a stunt consultant for a motion picture about a genetically synthesized prehistoric creature that escapes from captivity and terrorizes the city. The scene you are asked to review has the three characters of the movie being chased by the creature through an old warehouse. At the exit of the warehouse is a thick steel fire door 3.0 m high and 2.5 m wide with a mass of about 1760 kg. In the scene, the three actors are to flee from the building and close the door (initially at rest), thus sealing the creature inside the building. With the creature running at 17 m/s, they have only 8 seconds to shut the door. You are asked to determine if they can do it by calculating how long it would take them to actually close the door. You estimate that each actor can each push on the door with a force of 68 N. When they push together, actor needs a space of about 0.35 m between them and the next actor. To determine the moment of inertia, treat the mass of the door as being uniformly distributed. The door needs to rotate 130 degrees for it to dose completely. How long does it take to close the door?

Explanation / Answer

MI=1/3 b^3 h

=1/3. 25^3. 30=156250

Net torque= 68×25+68×24.65+68×24.3

=5028.6 max possible

s=0.5 a t^2

130deg=0.5 (torque/MI) t^2

2.2rad=0.5×5028.6/156250. t^2

t=37 sec

It takes the actors 37 sec approx to close the door

But they will not be able to stop the creature from escaping as per the data.

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