A helicopter is used to fill buckets with water to drop on fires. The bucket is

ID: 1331024 • Letter: A

Question

A helicopter is used to fill buckets with water to drop on fires.

The bucket is a hemisphere with a diameter of 2 meters and a

mass of 25 kg. The helicopter lowers the bucket into a lake or

reservoir to fill it.

a) What is the weight of a bucketful of water?

b) Assume the full bucket starts at rest and the helicopter

accelerates upward at 0.75 m/s2. Calculate the tension in

each of the five cables used to attach the bucket to the

helicopter.

c) The helicopter has a mass of 1960 kg. Calculate the lift force produced by each of the

four blades in order to allow the bucket-carrying helicopter to hover over the fire.

d) If the lift force from part c) is maintained once the water is dropped, how far does the

helicopter displace in 0.5 seconds?

(a)

Weight of bucket:

W =mg = ( 25 kg ) ( 9.8 m/s2) = 245 N

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(b)

Tension in 5 cables:

Apply Newton's second law

Tension and force that need to accelerate upward acts in upward direction and gravity acts downward

T - mg = ma

Solve for tension

T = m ( g + a ) = 25 kg ( 9.8 m/s2 + 0.75 m/s2 ) = 263.75 N

Tension produced in each of 5 cable:

T = 263.75 / 5 = 52.75 N

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