A cube of ice floats partly in water and partly in kerosene oil. The ratio of volume immersed in water to that in kerosene oil is:

Step 1: Define variables.
Let \( V_1 \) be the volume immersed in water and \( V_2 \) be the volume immersed in oil.
Step 2: Equilibrium condition.
\[ V_1 \rho_w g + V_2 \rho_o g = (V_1 + V_2) \rho_{{ice}} g \]
Step 3: Solve for ratio.
\[ V_1 + 0.8 V_2 = 0.9 (V_1 + V_2) \] \[ 0.1 V_1 = 0.1 V_2 \Rightarrow V_1 : V_2 = 1:1 \] The ratio of volumes immersed in water to oil is 1:1.
A particle is moving in a straight line. The variation of position $ x $ as a function of time $ t $ is given as:
$ x = t^3 - 6t^2 + 20t + 15 $.
The velocity of the body when its acceleration becomes zero is: