Quiz: Mechanical Engineering
Each question carries 1 mark
Negative marking: 1/4 mark
Time: 8 Minutes
Q1. In case of the nozzle, the effect of frictional losses is
(a) reduces the enthalpy of the fluid
(b) increases the enthalpy of the fluid
(c) no effect on enthalpy of the fluid
(d) None of the above
Q2. When a system reaches the state of equilibrium, the following property assumes its maximum value
(c) Gibbs function
(d) Helmholtz function
Q3. In aircraft, air refrigeration cycle is used because of
(a) low unit weight per tonne of refrigeration
(b) high heat transfer rate
(c) lower temperature at thigh-altitudes
(d) higher coefficient of performance
Q4. For a system to be in thermodynamic equilibrium the system and its surroundings
are to be in
(a) Thermal equilibrium
(b) Chemical equilibrium
(c) Mechanical equilibrium
(d) Thermal, chemical and mechanical equilibrium
Q5. In offset slider crank mechanism, the ratio of the working stroke time to the return
stroke time is
(a) less than 1
(b) equal to 1
(c) more than 1
(d) no specific range or value
Q6. The static friction
(a) bears a constant ratio to the normal reaction between the two surfaces
(b) is independent of the area of contact, between the two surfaces
(c) always acts in a direction, opposite to that in which the body tends to move
(d) all of the above
S1. Ans (a)
Sol. Frictional losses in the nozzle reduces the enthalpy of the fluid.
S2. Ans (b)
Sol. When system reaches equilibrium, driving force that executed the process becomes zero and entropy attains its maximum value. Moreover, as the process progress towards equilibrium the available energy or availability decreases continuously.
Sol. In aircraft, air refrigeration cycle is used because of low unit weight per ton of refrigeration. It is becoming obsolete because of their low coefficient of performance and high-power requirements.
S4. Ans (d)
Sol. A thermodynamic system will be in thermodynamic equilibrium with its surrounding when it is in thermal equilibrium (temperature is equal to surrounding), chemical equilibrium (chemical potential of system with respect to surrounding is zero) and mechanical equilibrium (Pressure of system is equal to that of surrounding) simultaneously.
Sol. A slider crank mechanism is a quick-return motion mechanism. In which return stroke
time is less than the forward stroke time
Sol. In case of static friction it is the ratio of Normal reaction between the surface to the friction force.
It is always opposing the motion or tending to motion of the body so always act in opposite direction.