Which of the following forces is/are fundamental in nature?

1. Gravitational force

2. Electromagnetic forces

3. Strong and weak nuclear forces

Select the correct answer using the code given below :

A spherical shell of outer radius R and inner radius R/2 contains a solid sphere of radius R/2 (see figure). The density of the material of the solid sphere is ρ and that of the shell is ρ/2. What is the average mass density of the larger sphere thus formed?

The human eye is like a camera that has a lens with :

A uniform meter scale of mass 0.24 kg is made of steel. It is kept on two wedges, W₁ and W₂, in a horizontal position. W₁ is at a distance of 0.2 m from one of its ends, while W₂ is at a distance of 0.4 m from the other end. If the force on the scale is N₁ due to W₁ and N₂ due to W₂, then : (take g = 10.0 m s⁻²)