Physics Practice Test – Density, Relative Density, Upthrust (Questions with Answers and Explanations)

A piece of cork floats in water because ________ (JAMB 2015)

A. the upthrust on it when completely immersed in water is greater than its weight in air
B. the surface of the water acts like an elastic skin
C. the upthrust on it when completely immersed in water is equal to its weight in air
D. there is no upthrust on it when it is completely immersed in water.

A balloon whose volume is 300 m³ is filled with hydrogen. If the density of air is 1.3 kgm^-3, find the upthrust on the balloon. [g = 10ms^-2] (JAMB 2012)

A. 3000 N     B. 3800 N     C. 3900 N     D. 4200 N

A piece of cork floats in a liquid. What fraction of its volume will be immersed in the liquid? [density of the cork = 0.25 x 10³ kgm^-3, density of liquid = 1.25 x 10³ kgm^-3] (JAMB 2013)

A. 0.1   B. 0.8   C. 0.5   D. 0.2