An Overhead Garage Door Has Two Springs,one on Each Side $20$

question 2

Multiple Choice

An overhead garage door has two springs,one on each side of the door (see figure) .A force of $20$ pounds is required to stretch each spring 1 foot.Because of a pulley system,the springs stretch only one-half the distance the door travels.The door moves a total of $x = 18$ feet,and the springs are at their natural length when the door is open.Find the combined lifting force applied to the door by the springs when the door is closed.​ ​

• A) \[\text { Combined lifting force } = 2 F = 356 \mathrm { lb }\]
• B) \(\text { Combined lifting force } = 2 F = 360 \mathrm { lb }\)
• C) \(\text { Combined lifting force } = 2 F = 362 \mathrm { lb }\)
• D) \(\text { Combined lifting force } = 2 F = 358 \mathrm { lb }\)
• E) \(\text { Combined lifting force } = 2 F = 364 \mathrm { lb }\)

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