Question

If there were a reduction in gravitational effect, which of the following forces do you think would change in some respect?
(A) Magnetic force
(B) Electrostatic force
(C) Viscous force
(D) Archimedes’ uplift

Answer 1

In this question, it says that if we reduce the gravitational effect which forces from the given forces will be affected. All the given forces are well known to us and we know the different factors governing the forces. We have to check which of the forces will have a direct or indirect relation with the gravitational effect.

Complete step by step solution:
Magnetic force can be defined as the force of attraction or repulsion between charged particles due to their motion.
Magnetic force can be mathematically expressed as,
$F = qvB\sin \theta$
Where $F$ stands for the magnetic force, $q$stands for the charge of the moving particle, $v$stands for the velocity of the moving particle, $B$stands for the magnetic field and $\theta$is the angle between the magnetic field vector and the velocity vector)
From the expression, we can see that the magnetic force does not depend on the gravitational effect.
The electrostatic force is also called the Coulomb force. It can be defined as the attractive force or repulsive force between two charged particles.
The electrostatic force can be expressed as,
$F = \dfrac{1}{{4\pi {\varepsilon _0}}}\dfrac{{{q_1}{q_2}}}{{{r^2}}}$
Where $F$stands for the electrostatic force, ${\varepsilon _0}$ stands for the permittivity of free space, ${q_1}$ and ${q_2}$ stands for the two charges and $r$ represents the distance between the two charges)
From this expression, we can see that the electrostatic force does not depend on the gravitational effect. Hence we can rule out the possibility of electrostatic force and magnetic force.
Viscous force can be defined as the force that tries to reduce the relative motion of two layers of liquids that are in contact.
We can mathematically express viscous force as,
$F = 6\pi \eta av$
Where $\eta$ stands for the viscosity of the fluid, $a$ stands for the radius of the particle experiencing the viscous force, $v$ stands for the velocity of the particle.
Here also it is clear that there is no relation between the viscous force and the gravitational effect. Hence the change in gravitational effect will not affect the viscous force.
According to Archimedes’ principle, when a body is fully or partially immersed in a fluid, the fluid will exert a force on the body and that force is known as the buoyant force.
This force can be expressed as,
$F = - \rho gV$
Where $F$ stands for the buoyant force, $\rho$ stands for the density of the fluid, $g$ stands for the acceleration due to gravity, and $V$stands for the volume of the fluid.
Here we can see that the buoyant force depends on the acceleration due to gravity. Acceleration due to gravity has a direct dependence on the gravitational effect. Hence we can say that it is the Archimedes uplift that is affected by the reduction in gravitational effect.
The answer is:

Therefore, the correct answer is Option (D): Archimedes’ uplift

Note:
This type of question can be answered very easily by looking at the options itself. Even if you don't know the expression for the buoyant force which is also called Archimedes' uplift you must be familiar with the expressions of magnetic force and electrostatic force hence you can directly rule out those two from the picture. Now we are left with just two options. From those two options by applying simple logic you can find that the answer is Archimedes' uplift. The name itself says uplift, so by seeing itself we can understand that the force has something to do with gravity. Hence we can conclude that the answer is Archimedes' uplift.