Hydraulics - Engineering

Q1:

A body of dimensions 1.5 m x 1.0 m x 2 m weighs 3000 kg in water. Its specific gravity is

A 0.8

B 0.9

C 1.0

D 1.1

ANS:D - 1.1

The specific gravity of a substance is defined as the ratio of the density of the substance to the density of water at a specified temperature. We can find the specific gravity (SG) of the body by using the relationship between the weight of the body in air (Wair​) and the weight of the body in water (Wwater​): SG=Wair​ / ​Wair​​-Wwater Given:

  • Dimensions of the body: 1.5m×1.0m×2m
  • Weight of the body in water: 3000kg
To calculate the weight of the body in air, we need to find its volume and then use the formula W=ρ×V×g, where W is the weight, ρ is the density, V is the volume, and g is the acceleration due to gravity. Given the dimensions of the body, its volume (V) is: V=l×b×ℎ=1.5 m×1.0 m×2 m=3 m^3 Now, let's calculate the weight of the body in air: Wair​=ρwater​×V×g=1000kg/m^3×3m^3×9.81m/s^2=29430N Now we can calculate the specific gravity: SG=Wair​ /Wair-−W water​​​=29430N / 29430N −3000N​ ≈ 29430/ 26430 ​≈1.113 So, the specific gravity of the body is approximately 1.1131.113. Therefore, none of the provided options match the specific gravity calculated.