Kiki is diving in salt water with a density of rho = 1025 kg/m^3. She has a mass
ID: 1561327 • Letter: K
Question
Kiki is diving in salt water with a density of rho = 1025 kg/m^3. She has a mass of 56.0 kg and a volume of 0.0570 m^3. a) What is her density? b) If she is completely submerged in the water, what weight would she have to add to herself to achieve neutral buoyance? (Assume the volume of the weight is negligible.) A plastic Pikachu figurine weighs 15.0 N in air and 7.0 N when completely submerged in fresh water. a) What is the volume of the figurine? b) What is the density of the figurine? (assume uniform density) c) The figurine doesn't actually "weigh" 7.0 N in water, this is its apparent weight. d) Hey wait a minute...(c) wasn't actually a question, it was a statement....what's going on here? Do we have to answer (c)? or(d)....?Explanation / Answer
(A) density = mass / volume
= 56 kg / 0.0570 m^3
=982.46 kg/m^3
(B) Bouyancy force = rho_fluid V_submerged g
= (1025) (0.0570) (g)
= 58.425 g
Weight force = m g = 56 g
Weight have to add = 58.425 - 56 = 2.425 g
= 2.425kg x 9.8 m/s^2
= 23.7 N ......Ans
4. (a) In water,
N = m g - Fb
7 = 15 - (1000 V g)
V = 8 / (1000 x 9.8) = 8.16 x 10^-4 m^3
(B) desnity = mass / volume = (15/9.8 kg) / (8.16 x 10^-4 m^3 )
= 1875 kg/m^3
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