ANS:B - is unsafe in shear

To determine the safety of the reinforced concrete beam in shear, we need to compare the actual shear stress induced by the applied shear force to the safe shear stress limit. Given:

• Width of the beam (b) = 25 cm
• Lever arm (d) = 40 cm
• Shear force (V) = 6 t/cm²
• Safe shear stress (safe​) = 5 kg/cm²

First, let's calculate the actual shear stress (τactual​) induced by the applied shear force using the formula: τactual​=b×dV​ Substituting the given values: τactual​=25cm×40cm6t/cm2​ τactual​=1000cm26t/cm2​ τactual​=0.006t/cm2 Now, let's convert the safe shear stress limit to the same unit as the actual shear stress (t/cm²): Safe shear stress=5 kg/cm2Safe shear stress=5kg/cm2 Since 1 kg = 0.001 t, we have: 5 kg/cm2=0.005 t/cm25kg/cm2=0.005t/cm2 Now, comparing the actual shear stress to the safe shear stress limit: τactual​=0.006t/cm2 Safe shear stress=0.005 t/cm2Safe shear stress=0.005t/cm2 Since the actual shear stress (τactual​) is greater than the safe shear stress limit (τsafe​), the beam is unsafe in shear. So, the correct answer is: The reinforced concrete beam is unsafe in shear.