Hello all, I am doing my homework right now and I need some help with some questions on my homework that I did not understand

It's multiple choice if that helps at all. If you could help show an explanation of how to get the correct answers or what formulas i should utilize. ANY help is greatly appreciated!

Here they are

1) The Pressure inside a commercial airliner is maintained at 1 atm(10^5 Pa). What is the net outward force exerted on a 1m x 2m cabin door if outside pressure is equal to .30 atm?

a)140, b) 1,400, c) 14,000 d) 140,000

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2)By what factor is the total pressure greater at a depth of 850m in water than at the surface where pressure is one atmosphere? (water density=1 x 10^3 kg/m^3, 1 atmosphereic pressure = 1.01 x 10%5 N/m^2, and g=9.8)

a)100, b)83, c)74, d)19

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3) Water is being sprayed from the nozzle of hose diameter 2 cm. The nozzle has an opening of .50 cm, and water leaves the hose at a speed of 10 m/s. What is the speed of the water in the hose?

a).63 m/s, b).80 m/s, c)2.5 m/s, d) 10 m/s

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4)A cube of wood with a density of .78 g/cm^3 is 10cm on a side. When placed in water, what height will the cube float above the surface of the water?

a)7.8 cm, b) 5 cm, c)2.2 cm, d)6.4cm

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5)The pressure of 20g of an ideal monatomic gas is tripled while the volume is halved. What happens tot he internal energy?

a)It stays the same b) Increases c) Decreases d)Indeterminate

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6) A solar heating system has 25% conversion efficiency. Solar radiation incident on solar panels is 1000 w/n^2. What is the increase in temperature of 30kg in a 1 hr period by a 4.0 m^2 area collector?

a) 14.2 C b) 22.4 C, c)28.7 C d) 44.3 C

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7) Area on a p-v diagram has units associated with

a) energy, b) momentum c) temperature d) change in temp

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8) A system acted on by surroundings receives 50J of heat while doing 20J of work. What is the net change of internal energy?

a) 70 b) 30 c) 0 d) -30