Two forces
A) Which of the following is velocity ratio?
B) [tex]\frac{ Ld }{ Ed }[/tex]
(C) [tex]\frac{ Ed }{ Ld }[/tex]
D) [tex]\frac{E}{L}[/tex]
A) [tex]\frac{L}{E}[/tex]
Which of the following is affected by friction?
A) VR
B) efficiency
C) MA
D) B and C both
Which of the following work is done by effort?
A) input work
B) output work
C) resultant work
D) useful work
Which of the following has 100% efficiency?
A) hydraulic machine
B) perfect machine
C) simple machine
D) compound machine
Velocity ratio of which machine is given by [tex]\frac{-}{h}[/tex]?
A) lever
B) inclined plane
D) wheel and axle
Answer (2)
Velocity ratio is the ratio of effort distance to load distance: L d E d .
Friction affects both efficiency and mechanical advantage.
Input work is the work done by the effort.
A perfect machine has 100% efficiency.
The velocity ratio of an inclined plane is given by h e i g h t l e n g t h .
( c ) , D , A , B , B
Explanation
Problem Analysis Let's analyze each question step by step.
Velocity Ratio Question 1: The velocity ratio (VR) is defined as the ratio of the distance traveled by the effort to the distance traveled by the load. Therefore, VR = L o a d D i s t an ce E ff or t D i s t an ce which is L d E d . The correct option is (c).
Effect of Friction Question 2: Friction is a force that opposes motion. It affects both efficiency and mechanical advantage (MA). Efficiency is reduced because some of the input work is converted into heat due to friction. MA is also affected because a greater effort is required to overcome friction. Therefore, the correct option is D) B and C both.
Work Done by Effort Question 3: The work done by the effort is the input work. The effort is the force applied to the machine, and the input work is the work done by this force. Therefore, the correct option is A) input work.
100% Efficiency Question 4: A perfect machine is a theoretical machine that has 100% efficiency. In reality, no machine is perfectly efficient due to friction and other losses. Therefore, the correct option is B) perfect machine.
Velocity Ratio of Inclined Plane Question 5: The velocity ratio of an inclined plane is given by the formula VR = h e i g h t l e n g t h . The question provides the expression h − , which corresponds to h e i g h t l e n g t h . Therefore, the correct option is B) inclined plane.
Final Answers Final Answers:
(c) L d E d
D) B and C both
A) input work
B) perfect machine
B) inclined plane
Examples
Understanding velocity ratio, efficiency, and work done by machines is crucial in various real-life applications. For example, when designing a ramp (inclined plane) to move heavy objects, knowing the velocity ratio helps determine the effort required. Similarly, understanding the impact of friction on efficiency helps in optimizing machine designs to minimize energy loss. These concepts are also fundamental in understanding how levers, pulleys, and other simple machines work, enabling us to perform tasks more efficiently.
The answers to the questions are as follows: 1) (C) L d E d , 2) (D) B and C both, 3) (A) input work, 4) (B) perfect machine, and 5) (B) inclined plane.
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