JAMB - Physics (2017 - No. 5)
Calculate the upthrust on an object of volume 50cm3 which is immersed in liquid of density \(10^{3}\) kgm-3 [g = 10ms-2]
0.8N
2.5N
0.5N
1.0N
Explanation
Upthrust = change in weight
density = \(\frac{\text{mass}}{\text{volume}}\)
Mass of liquid displaced = Density of Liquid × Volume;
= \(10^{3} \times 50 \times 10^{−6}m^{3}\)
= 0.05kg
(Note that the volume of \(50cm^{3}\) was converted to \(m^{3}\) by multiplying by \(10^{6}\)) i.e \(50cm^{3} = 50 \times 10^{−6}m^{3}\)
Since mass displaced = 0.05kg
Upthrust = mg = 0.05 × 10
= 0.5N
density = \(\frac{\text{mass}}{\text{volume}}\)
Mass of liquid displaced = Density of Liquid × Volume;
= \(10^{3} \times 50 \times 10^{−6}m^{3}\)
= 0.05kg
(Note that the volume of \(50cm^{3}\) was converted to \(m^{3}\) by multiplying by \(10^{6}\)) i.e \(50cm^{3} = 50 \times 10^{−6}m^{3}\)
Since mass displaced = 0.05kg
Upthrust = mg = 0.05 × 10
= 0.5N
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