NHPC JE'21 ME: Daily Practices Quiz. 21-Nov-2021

Quiz: Mechanical Engineering
Exam: NHPC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. Consider the statements for a CNC lathe machine
1. The X-axis controls the cross-slide motion of the cutting tool
2. The Z-axis controls the travel of the carriage towards or away from the headstock
3. The Y-axis controls the motion of the job
4. The X-Y-Z axes are used for rotational movement of the table
Which of the above statements are correct?
(a) 1 and 3
(b) 1 and 2
(c) 3 and 4
(d) 2 and 3

Q2. Which of the following is incorrect for NC machine tool?
(a) Instruction undergoes electronic processing and outcome is the pulsed command
(b) Control unit sends signals to drive unit of machine tool and to magnetic box
(c) Instruction for manufacturing the components is written in coded language and read by tape recorder
(d) All of the above

Q3. During throttling process
(a) Enthalpy does not change
(b) Pressure reduces
(c) Volume does not change
(d) Both (a) and (b)

Q4. If H be the heat supplied to the system to do work W and change in internal energy as ∆U, then,
(a) H = ∆U + W
(b) ∆U = H + W
(c) W = H + ∆U
(d) H = W/∆U

Q5. Maximum shear strain occurs on a plane which are
(a) Principal planes
(b) Inclined at 45° with principal planes
(c) 90° with principal planes
(d) All of above

Q6. Shear span is defined as the zone where:
(a) bending moment is zero
(b) shear force is zero
(c) shear force is constant
(d) bending moment is constant

Solution

S1. Ans. (b)
Sol. For lathes machine, the X-axis controls the motion of the cross-slide at a right angle to the spindle axis.
Generally, CNC lathes are two-axis machines i.e., X-axis and Z-axis and have no Y-axis.
The axis of motion that is parallel to the spindle axis is always the Z-axis. The Z-axis controls the travel of the carriage towards or away from the headstock

S2. Ans. (d)
Sol. All of the above statements are correct.

S3. Ans. (d)
Sol. Throttling process is used to reduce pressure of fluid from higher pressure to lower pressure by keeping enthalpy constant.

S4. Ans. (a)
By First law of thermodynamics, the change in internal energy is equal to Heat added minus work by the system.
It also states that energy must be conserved for any system.

S5. Ans.(b)
Sol. Maximum shear strain occur on 45° with the principal planes.

S6. Ans.(c)
Sol. Shear span is the distance from the point of application of concentrated force to its respective reaction force. throughout shear span the shear force is constant.
“Shear span is defined as the zone where shear force is constant.”