  # ISRO Scientist or Engineer Mechanical 2011

Instructions

For the following questions answer them individually

Question 21

# If two objects are weighed in water and both of them lose the same weight, then the two objects must have identical Question 22

# 1kg of moist air of RH 70% at $$21^\circ C$$ is cooled at constant pressure of 1 bar to $$5^\circ C.$$ The vapour pressure at $$21^\circ C$$ and $$5^\circ C$$ are 0.025 bar and 0.0087 bar. The percentage of water vapour that condenses into water, at $$5^\circ C$$ is Question 23

# Two spherical balis of same material and surface finish have their diameters in the ratio of 2:1. Both are heated to same temperature and allowed to cool by radiation. Rate of cooling of big ball as compared to smaller one will be in the ratio of Question 24

# Ninety kilograms of ice at $$0^\circ C$$ are completely melted. Find the entropy change, in kJ/K, if $$T_2 = 0^\circ C.$$ (Latent heat of fusion is 318.5 kJ/kg.K) Question 25

# A solid shaft of 100mm diameter transmits 160 HP at 200rpm. The modulus of rigidity $$c = 8 \times 10^5 kg/cm^2$$ .Then the maximum angle of twist for a length of 6 meteris Question 26

# A perfect gas at $$27^\circ C$$ is heated at constant pressure till its volume is double. The final temperature is Question 27

# The stagnation temperature of an isentropic flow of air (k = 1.4) is 360 K. If the temperature is 200 K at a section, then the Mach numberof the flow will be Question 28

# Air at $$20^\circ C$$ blows over a plate of $$50 cm \times 75 cm$$ maintained at $$250^\circ C.$$ If the convection heat transfer coefficient is $$25W/m^{2^\circ} C$$ , the heat transfer rate is Question 29

# A small plastic boat loaded with pieces of steel rods is floating in a bath tub. If the cargo is dumped into the water allowing the boatto float empty, the water level in the tub will Question 30

# When a jet plane flying at 300 m/s is at the very top of its trajectory, the apparent weight of a passenger is one half of her actual weight. Find the radius of curvature R of the flight path at this point. Use $$g = 10 m/s^2.$$  OR