Question

Choose the correct statement
A. In a simple machine, input energy is always equal to output energy.
B. actual mechanical advantage > ideal mechanical advantage.
C. $velocity\text{ }ratio\text{ }=\dfrac{Displacement\text{ }of\text{ }the\text{ }effort}{Displacement\text{ }of\text{ }the\text{ }load}$
D. The mechanical advantage of a single fixed pulley is greater than one.

Answer 1

The velocity ratio of a machine is defined as the ratio of distance moved by the effort to the distance moved by the load.

Complete step by step answer:
Option A: In a simple machine the input energy is always greater than the output energy as some of the energy is dissipated in the form of heat due to friction. Therefore, this is the incorrect option.
Option B: The actual mechanical advantage (AMA) is given as the ratio of the output force ${{F}_{0}}$ to the input force${{F}_{1}}$.
$AMA=\dfrac{{{F}_{0}}}{{{F}_{1}}}$
Most machines have actual mechanical advantages greater than one.
The ideal mechanical advantage (IMA) is given as the ratio of input distance ${{D}_{1}}$ to the output distance ${{D}_{0}}$
$IMA=\dfrac{{{D}_{1}}}{{{D}_{0}}}$
Also, greater than AMA, because like AMA it doesn’t take into account the forces of friction.
So, IMA > AMA. Therefore, this is the incorrect option.
Option C: As you know, linear displacement is the same as distance. So, the velocity ratio can be seen as the ratio of displacement of the effort to the displacement of the load.
i.e. velocity ratio = Displacement of the effort Displacement of the load. Therefore, this is the correct option.
Option D: The mechanical advantage of a pulley is only depending on the number of ropes. Here you have given a simple pulley so the number of ropes is one.
Then, IMA=1.
Therefore, this is the incorrect option.

Note: In reality the force of friction acts and ideally, they ignore this force of friction. The real output is always less than the ideal output.