School of Aerospace Engineering
Thermal Science (18AS41) – Batch 2019
Unit I
Assignment 1
1. A gas is contained in a vertical, frictionless piston– cylinder device. The piston has a
mass of 3.2 kg and a cross sectional area of 35 cm2. A compressed spring above the
piston exerts a force of 150 N on the piston. If the atmospheric pressure is 95 kPa,
determine the pressure inside the cylinder.
2. A vertical, frictionless piston–cylinder device contains a gas at 180 kPa absolute
pressure. The atmospheric pressure outside is 100 kPa, and the piston area is 25 cm2.
Determine the mass of the piston.
3. The pilot of an airplane reads the altitude 6400 m and the absolute pressure 45 kPa
when flying over a city. Calculate the local atmospheric pressure in that city in kPa and
in mmHg. Take the densities of air and mercury to be 0.828 kg/m3 and 13,600 kg/m3,
respectively.
4. The drag force exerted on a car by air depends on a dimensionless drag coefficient, the
density of air, the car velocity, and the frontal area of the car. That is, FD = FD(Cdrag,
Afront, ρ, V). Based on unit considerations alone, obtain a relation for the drag force.
Air Velocity
5. The atmospheric pressures at the top and the bottom of a building are read by a
barometer to be 96.0 and 98.0 kPa. If the density of air is 1.0 kg/m3, Estimate the height
of the building.
6. An escalator was designed to move 10 people, 85 kg each, at a constant speed of 0.2
m/s at 60° slope. Determine the minimum power input needed to drive this escalator.
What would be the maximum power required if I need to double the escalator velocity?
7. An electric heater has a resistance of R = 50 ohms. It is connected across a power
supply of V = 240 V, for a period of t = 2 hr. Determine the work done (W) by the
power supply on the heater. How many units of electricity are consumed?
8. The pressure of the gas contained in the piston–cylinder assembly of Figure below
varies with its volume according to p = A+ (B/V), where A, B are constants. If
pressure is in lbf/ft2 and volume is in ft3, what are the units of A and B?
Thermal Science (18AS41) – Batch 2019
Unit I
Assignment 1
1. A gas is contained in a vertical, frictionless piston– cylinder device. The piston has a
mass of 3.2 kg and a cross sectional area of 35 cm2. A compressed spring above the
piston exerts a force of 150 N on the piston. If the atmospheric pressure is 95 kPa,
determine the pressure inside the cylinder.
2. A vertical, frictionless piston–cylinder device contains a gas at 180 kPa absolute
pressure. The atmospheric pressure outside is 100 kPa, and the piston area is 25 cm2.
Determine the mass of the piston.
3. The pilot of an airplane reads the altitude 6400 m and the absolute pressure 45 kPa
when flying over a city. Calculate the local atmospheric pressure in that city in kPa and
in mmHg. Take the densities of air and mercury to be 0.828 kg/m3 and 13,600 kg/m3,
respectively.
4. The drag force exerted on a car by air depends on a dimensionless drag coefficient, the
density of air, the car velocity, and the frontal area of the car. That is, FD = FD(Cdrag,
Afront, ρ, V). Based on unit considerations alone, obtain a relation for the drag force.
Air Velocity
5. The atmospheric pressures at the top and the bottom of a building are read by a
barometer to be 96.0 and 98.0 kPa. If the density of air is 1.0 kg/m3, Estimate the height
of the building.
6. An escalator was designed to move 10 people, 85 kg each, at a constant speed of 0.2
m/s at 60° slope. Determine the minimum power input needed to drive this escalator.
What would be the maximum power required if I need to double the escalator velocity?
7. An electric heater has a resistance of R = 50 ohms. It is connected across a power
supply of V = 240 V, for a period of t = 2 hr. Determine the work done (W) by the
power supply on the heater. How many units of electricity are consumed?
8. The pressure of the gas contained in the piston–cylinder assembly of Figure below
varies with its volume according to p = A+ (B/V), where A, B are constants. If
pressure is in lbf/ft2 and volume is in ft3, what are the units of A and B?
