Engineering Mechanics MCQ Questions & Answers | Mechanical Engineering

Option A: Mechanical advantage is greater than velocity ratio
In an ideal machine, there are no energy losses due to friction or other resistances.
Therefore, the mechanical advantage cannot be greater than the velocity ratio because that would imply the machine is creating additional energy, which is impossible in an ideal system.

Option B: Mechanical advantage is equal to velocity ratio
In an ideal machine, the mechanical advantage (MA) is equal to the velocity ratio (VR) because all the input energy is fully transmitted to the output without any losses.
This equality holds true as there are no inefficiencies in an ideal machine.

Option C: Mechanical advantage is less than velocity ratio
In real machines, due to energy losses, the mechanical advantage is often less than the velocity ratio.
However, in ideal machines, where no losses are assumed, the mechanical advantage should equal the velocity ratio, not be less than it.

Option D: Mechanical advantage is unity
While mechanical advantage can be unity in specific scenarios, it is not a general characteristic of all ideal machines.
An ideal machine’s mechanical advantage will match the velocity ratio, but the value is not limited to unity.

Conclusion:
The correct answer is Option B: Mechanical advantage is equal to velocity ratio.
In an ideal machine, mechanical advantage equals the velocity ratio due to the absence of energy losses.

Angle of Friction:
The angle of friction is the angle at which a body just begins to move down an inclined plane. It represents the maximum angle at which a body can rest on the inclined plane without sliding down. It is determined by the coefficient of friction between the surfaces in contact.

Angle of Repose:
The angle of repose is the maximum angle at which a pile of granular material remains stable without sliding or collapsing. It is the natural angle formed by loose particles such as sand, gravel, or powders when poured onto a flat surface. The angle of repose depends on factors such as the size, shape, and cohesion of the particles.

While both angles relate to the stability of objects on surfaces, they describe different scenarios: the angle of friction pertains to solid bodies on inclined planes, while the angle of repose relates to granular materials forming natural slopes.

Given the context of the question, which is about the angle at which a body begins to move down an inclined plane, the correct answer remains Option A: Angle of friction.