WAEC - Physics (1993 - No. 8)
A block of material of volume 2 X 10\(^{-5}\)m\(^3\) and density 2.5 x 10\(^3\) kgm\(^{-3}\) is suspended from a spring balance with half volume of the block immersed in water. What is the reading of the spring balance? (Density of water =1.0x10\(^3\) kg m\(^{-3}\) g = 10 ms\(^{-2}\)).
0.10N
0.25N
0.30N
0.40N
0.50N
Explanation
Weight of object = mg
= \(\rho vg\) = 2.5 x 10\(^3\) x 2 x 10\(^{-5}\) x 10 = 0.5N;
Upthrust = weight of displaced fluid = \(\rho_{water} vg\)
= \(\frac{1.0 \times 10^3 \times 2 \times 10^{-5} \times 10}{2}\) = 0.1N
∴Reading = 0.5 – 0.1 = 0.4N
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