Please help me answer these questions. 1) A small ferryboat is 3.70 m wide and 5

Question

Please help me answer these questions.

1) A small ferryboat is 3.70 m wide and 5.50 m long. When a loaded truck pulls onto it, the boat sinks an additional 3.70 cm into the river. What is the weight of the truck?

2) A spherical weather balloon is filled with hydrogen until its radius is 2.70 m. Its total mass including the instruments it carries is 12.0 kg.

(a) Find the buoyant force acting on the balloon, assuming the density of air is 1.29 kg/m3.
kN

(b) What is the net force acting on the balloon and its instruments after the balloon is released from the ground?
kN

(c) Why does the radius of the balloon tend to increase as it rises to higher altitude?

Because the external pressure  (increases or decreases) with increasing altitude.?

Explanation / Answer

1)   weight of the truck = (370 * 550 * 3.70)/1000

                                    = 752.95 Kg

                                    =    7378.91 N

2)     V=4/3(pi)r3

=> V=4/3*(3.14)*(2.7)3 = 82.406    m3

=>   F(air)=(density of air)*(volume displaced)*(gravity)

a)    F = (1.29)*( 82.406)*(9.8)    =    1041.77 N

b)    F(net)=F(air) - Fg(balloon)

   =>   F(net) = 1041.77 N - (12 x 9.8) = 924.17 N     (upward)

c)   The balloon gets bigger because the air pressure decreases

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