Question

The door of an almirah is 6ft high, 1.5 ft wide and weights 8 kg. The door is supported by two hinges situated at a distance of 1 ft from the ends. Assuming forces exerted on the hinges are equal, the magnitude of the force is

• A. 15 N
• B. 10 N
• C. 28 N
• D. 43 N

Answer 1

Answer: (D)

43 N

Answer 2

tan θ = $\frac{2}{3/4} = \frac{8}{3}or\cos\theta = \frac{3}{\sqrt{73}}$

Taking torque about O

8g$\left( \frac{3}{4} \right)$ = 4F cos Q

6g = 4F$\left( \frac{3}{\sqrt{73}} \right)or ⥂ F = 5\sqrt{73} = 43N$