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1. a piece of lead has a shape of a hockey puck with a diameter of 7.5cm and a height of 2.5cm. If the puck is placed in a mercury bath it floats. how deep below the surface of the mercury is the bottom of the lead puck? [2.1cm]

(can anyone give me some starters help with this, like guide me in the right direction becuase im really clueless about this one)

2. a garden hose is attached to a water faucet on one end and a spray nozzle on the other end. The water faucet is turned on but the nozzle is turned off so that no water flows through the hose. The hose lies horizontally on the ground and a stream of water sprays vertically out of a small leak to a hieght of 0.75m. What is the pressure inside the hose? [ans: 7.4kPa]

(i really have absolutely no idea with this because this is to do with bernoulli's equation but i really still don't have a clue)

3. A 0.12kg balloon is filled with helium (density = 0.719kg/m^3). if the balloon is a sphere with a radius of 5.2m, what is the maximum weight it can lift? [ans: 5.7kN]

(with this question, i tried finding the mass of the inside of the balloon by m = density x volume...where density = 0.179, and volume = 4/3 pi r^3...where r = 5.2...and my answer came out to be 105.43kg...multiplying that by 9.8 but that does not give me the right answer...so can anyone see what im doing wrong?)