MACHINES

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• Q1: Define Machine.
  Ans: A machine is a device or combination of mechanisms that transmits and transforms energy to perform useful work.
• Q2: Write the advantages of machines.
  Ans: The advantages of machines are:

  • ➔ It reduces human effort
  • ➔ It increases efficiency and speed of work
  • ➔ It saves time
  • ➔ It improves accuracy of work
  • ➔ It helps in performing heavy tasks easily
• Q3: Define Mechanism.
  Ans: A mechanism is a kinematic chain in which one link is fixed and the others move relative to it to produce a desired motion.
• Q4: State the types of Mechanism.
  Ans: The types of mechanism are:

  • ➔ Simple mechanism
  • ➔ Compound mechanism
• Q5: Define Simple Mechanism.
  Ans: A simple mechanism is a mechanism formed by a single kinematic chain with one fixed link.
• Q6: Define Compound Mechanism.
  Ans: A compound mechanism is formed by combining two or more simple kinematic chains.
• Q7: State the principle of Work.
  Ans: The principle of work states that work done on a machine is equal to work done by the machine (in an ideal case).
• Q8: Define Mechanical Advantage. Write the formula to calculate it.
  Ans: Mechanical Advantage is the ratio of load to effort in a machine.
  
  Formula:
  
  MA = Load / Effort
• Q9: Define Load.
  Ans: Load is the resistance or weight that is lifted or moved by a machine.
• Q10: Define Effort.
  Ans: Effort is the force applied on a machine to move or lift the load.
• Q11: Define Velocity Ratio. Write the formula to calculate Velocity Ratio.
  Ans: Velocity Ratio is the ratio of distance moved by effort to the distance moved by load.
  
  Formula:
  
  VR = Distance moved by effort / Distance moved by load
• Q12: Define Input. Write the formula to calculate Input.
  Ans: Input is the work done on a machine by applying effort.
  
  Formula:
  
  Input = Effort × Distance moved by effort
• Q13: Define Output. Write the formula to calculate Output.
  Ans: Output is the useful work done by the machine on the load.
  
  Formula:
  
  Output = Load × Distance moved by load
• Q14: Define Efficiency of Machine. Write the formula to calculate it.
  Ans: Efficiency is the ratio of output work to input work of a machine.
  
  Formula:
  
  η = (Output / Input) × 100%
• Q15: Define Ideal Machine.
  Ans: An ideal machine is a machine in which there is no loss of energy and efficiency is 100%.
• Q16: Define Reversibility of Machines.
  Ans: A reversible machine is a machine that can work in both directions, i.e., input can produce output and output can move back the machine.
• Q17: State the Law of Machine.
  Ans: The law of machine states that effort required is a linear function of load.
  
  Formula:
  
  P = mW + C
  
  where:
  P = effort
  W = load
  m and C are constants
• Q18: Define Single Purchase Crab.
  Ans: A single purchase crab is a lifting machine in which one load is lifted by a single set of gears or pulleys using manual effort.
• Q19: State the uses of Single Purchase Crab.
  Ans: The uses of single purchase crab are:

  • ➔ Used for lifting light loads
  • ➔ Used in small workshops
  • ➔ Used in construction sites for general lifting work
  • ➔ Used where less mechanical advantage is required
• Q20: Define Double Purchase Crab.
  Ans: A double purchase crab is a lifting machine that uses two sets of gears to reduce effort required to lift heavy loads.
• Q21: State the uses of Double Purchase Crab.
  Ans: The uses of double purchase crab are:

  • ➔ Used for lifting heavy loads
  • ➔ Used in large workshops and industries
  • ➔ Used in shipyards and construction works
  • ➔ Used where high mechanical advantage is required
• Q22: Define Worm and Worm Wheel.
  Ans: A worm and worm wheel is a gear system in which a screw (worm) drives a toothed wheel, used to achieve high reduction in speed.
• Q23: Define Screw Jack.
  Ans: A screw jack is a device used to lift heavy loads by applying small effort through screw motion.
• Q24: Define Differential Screw Jack.
  Ans: A differential screw jack is a modified screw jack that uses two different screw threads to reduce effort required for lifting load.
• Q25: State the uses of Screw Jack.
  Ans: The uses of screw jack are:

  • ➔ Lifting vehicles
  • ➔ Heavy machinery maintenance
  • ➔ Construction work
• Q26: Define Differential Pulley.
  Ans: A differential pulley is a lifting device that uses chain and pulleys of different diameters to lift heavy loads with less effort.
• Q27: State the uses of Differential Pulley.
  Ans: The uses of differential pulley are:

  • ➔ Workshops
  • ➔ Factories
  • ➔ Material handling systems
• Q28: Define Wheel and Axle.
  Ans: Wheel and axle is a simple machine in which a large wheel is attached to a smaller axle to multiply force.
• Q29: State the uses of Wheel and Axle.
  Ans: The uses of wheel and axle are:

  • ➔ Steering wheels
  • ➔ Winches
  • ➔ Door knobs
• Q30: Define Differential Wheel and Axle.
  Ans: A differential wheel and axle is a modified machine that provides higher mechanical advantage by using two wheels of different radii.
• Q31: Describe the working principle of Simple Wheel and Axle.
  Ans: The simple wheel and axle works on the principle of turning effect of force (moment).
  
  When effort is applied on the wheel, it rotates the axle due to rigid connection between them.
  The wheel has a larger radius, and the axle has a smaller radius.
  
  Because of this difference in radii, a small effort applied on the wheel produces a large lifting force on the axle.
  
  This helps in lifting or moving heavy loads easily by using less effort.
• Q32: Write the velocity of a Differential Screw Jack.
  Ans: Velocity ratio of a differential screw jack is given by:
  VR = (2πR) / (p₁ - p₂)
  where R = length of handle, p₁ and p₂ are pitches of screws