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On takeoff, the combined action of the engines and wings of an airplane exerts an 8000N force on the plane, directed upward at an angle of 65* above the horizontal. The plane rises with constant velocity in the vertical direction while continuing to accelerate in the horizontal direction.

a) What is the weight of the plane ?

b) What is its horizontal acceleration ?

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V (initial)= 0

weight = mass time gravity

weight = 9.8 time mass

acceleration in vertical direction = 0 (constant speed)

F (apply) = 8000 N

From F = ma --> m = F / a

And I stuck at this point !

#2

Two blocks are fastened to the ceiling of an elevator. Each block is 10 kg. The elevator accelerates upward at 2 m/s2 (at the block that close to the ceiling). Find the tension in each rope.

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F (upper) = 100 N

F (lower) = 100 * 2 = 200 N

#3

A 72 kg man stands on a spring scale in an elevator. Starting from rest, the elevator ascends, attaining its maximum speed of 1.2 m/s in .80s. It travels with this constant speed form 5 s, undergoes a uniform negative acceleration for 1.5 s and comes to rest. What does the spring scale registered (a) before the elevator starts to move ? (b) during the first .8 s ? (c) while the elevator is traveling at constant speed ? (d) during the negative acceleration ?

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a) Weight = 72*9.8 = 705.6 N because Fg = m*g

b) From V (intial) = 0 V (final) = 1.2 m/s t = .8 s

so a = 1.5 m/s2.

F = 705.6 + F (that is accelerating) ==> 705.6 + 72 (1.5) = 813.6 N

c) 705.6 N

d) I don't get what is this say "undergoes a uniform negative acceleration for 1.5 s and comes to rest"

Help Please ? Thanks

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# Homework Help: Force - Scale - Tension

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