Answer:
a) 3.37 x 
b) 6.42kg/
Explanation:
a) Firstly we would calculate the volume of the metal using it`s weight in air and water , after finding the weight we would find the density .
Weight of metal in air = 50N = mg implies the mass of metal is 5kg.
Now the difference of weight of the metal in air and water = upthrust acting on it = volume (metal) p (liquid) g = V (1000)(10) = 14N. So volume of metal piece = 14 x
. So density of metal = mass of metal / volume of metal = 5 / 14 x
= 3.37 x 
b) Water exerts a buoyant force to the metal which is 50−36 = 14N, which equals the weight of water displaced. The mass of water displaced is 14/10 = 1.4kg Since the density of water is 1kg/L, the volume displaced is 1.4L. Hence, we end up with 3.57kg/l. Moreover, the unknown liquid exerts a buoyant force of 9N. So the density of this liquid is 6.42kg/
Answer:
0.5 m/s
Explanation:
Using conservation of momentum, P1=P2, the system starts off with zero momentum as nothing is moving. But in the second part of the equation(P2) the child throws the package to the right. By Newton's third law, the child and the boat should move to the left. Plugging in what we know, 0= -90v + 6kg*8m/s. Solving for v you will get 0.5 meters per second. The mass is 90kg as that the is mass of the child and boat combined. I also made it negative as the boat and child move left (I designated this as the negative direction) and the package's momentum is positive as it is moving to the right.