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This is the second of our many quizzes on Machines . Click on this to access more such competitive quizzes on Mechanics.

Machines Quiz 2

physics

In our practical life, no machine will be having $100\%$ efficiency. State the reason for this. 

The friction will be there in practical life other than ideal situations. 

 Since a machine's moving parts are not perfectly smooth, the string is not perfectly elastic, and the moving parts of a machine have some weight, no machine can work at $100\%$ performance.

Find out the mechanical advantage if the velocity of effort be $12\text{ }m{{s}^{-1}}$ and velocity of load be $4\text{ }m{{s}^{-1}}$ in a machine of efficiency $70\%$? 

The product of the velocity ratio and efficiency would be the mechanical advantage.

 $\text{The mechanical advantage,}\\  MA=VR\times \eta\\  \text{The velocity ratio will be,}\\\text{VR=}\dfrac{\text{Velocity of effort}}{\text{Velocity of load}} \\\Rightarrow VR=\dfrac{12}{4}=3 \\  \Rightarrow VR=3 \\\text{Substituting the values in it,}\\ MA=3\times \dfrac{70}{100} \\\therefore MA=2.1$

The number of teeth of the driving wheel of the machine made by Anandhu  is $36$. The number of the teeth of the driven wheel has been mentioned as $4$. What will be the gear ratio in this condition? 

 The ratio of the number of teeth in the driving wheel to the number of teeth in the driven wheel is known as the gear ratio.

$\text{The gear ratio will be given as,}\\  \text{Gear ratio}=\dfrac{{{N}_{A}}}{{{N}_{B}}}\\\text{Substituting the values in it,}\\\text{Gear ratio}=\dfrac{36}{4} \\  \therefore \text{Gear ratio}=9$

 Meera and Arun had an argument on a nutcracker as in which class of lever it can be placed.Meera told that it is in class 1 type and Arun strongly opposed Meera saying that it is a class 3 type. Who is actually correct? 

The fulcrum will be at one end. At this place, two metal rods of the device will be hinged together. The effort will be applied at the opposite ends of the rods. The resistance force by the nut to be cracked lies in the centre. Therefore class 2 levers. 

The length of an inclined plane has been given as $3\text{ }m$. And the height of the inclined plane has been mentioned as $1\text{ }m$. What will be the velocity of the load if the velocity of effort is $8\text{ }m{{s}^{-1}}$ for a machine of efficiency $75\%$ ? 

The velocity ratio is the ratio of the effort velocity to the load velocity.

$\text{The Mechanical advantage of the inclined plane will be,}\\  MA=\dfrac{l}{h}\\  \text{Substituting the values in it,}\\  MA=\dfrac{3}{1}=3\\  \text{The efficiency will be,}\\\eta =\dfrac{MA}{VR}\times 100\\  \text{Substituting the values in it,}\\  0.75=\dfrac{3}{VR} \\  \Rightarrow VR=4 \\  \text{The velocity ratio will be,}\\ VR=\dfrac{{{V}_{e}}}{{{V}_{l}}}\\\text{Substituting,}\\ 4=\dfrac{8}{{{V}_{l}}} \\\therefore{{V}_{l}}=2\text{ }m{{s}^{-1}}$ 