ICHE Chapter 2

Which of these is/are a unit?

• gmol

• velocity

• density

• degree Rankine, °R

Answer explanation

The units gmol and degree Rankine, °R, are considered units of measurement, while velocity and density are dimensions.

What are the units for length, mass, time and temperature in the FPS system?

• meter, gram, second, degree Rankine

• foot, pound, hour, degree Fareinheit

• foot, pound, second, degree Rankine

• foot, kilogram, second, kelvin

Answer explanation

In the FPS system, the units for length, mass, time, and temperature are (F) foot, (P) pound, (S) second, and degree Rankine respectively.

Which of these equations are true?

• Force = Mass x Acceleration

• Work done = Power / Time

• Acceleration = Velocity / Time

• Energy = Force x Distance

Answer explanation

Power = Work done / Time OR Energy / Time.

The remaining equations are all true.

What is the SI unit for energy?

• W

• m

• J

• N

Answer explanation

The SI unit for energy is J, which stands for Joule. It is named after the physicist James Prescott Joule.

Water flows into a tank at a rate of 18,000 L/h. Convert this into m³/s.

(Submit your answer without the units.)

Answer explanation

Recall that 1m³ = 1000L, and 1h = 3600s.

The correct workings should be:

18,000 L/h ÷ 1000 L/m³ ÷ 3600 s/h

Water is charged into a tank of radius 1 m. The level in the tank rises at a rate of 0.5 m per second. What is the volumetric flowrate of water (in m³/s) entering the tank?

(Submit your answer in 2 decimal places, without the units.)

Answer explanation

The question asks you for the volumetric flowrate. This suggests that you need to calculate the volume of water entering the tank per time.

The tank has a radius of 1 m, and water is rising at 0.5 m/s. To find the volume of this water, we need to use the cross-sectional area of the tank:

πr² x h

= π (1 m)² x 0.5 m/s

= 1.57 m³/s

Convert 50 lb_m/ft² to kg/m².

• 10.24

• 74.41

• 244.12

• 1186.48

Answer explanation

The conversion factors to use for this question are:

1 kg = 2.2046 lb

1 m = 3.2808 ft

Make sure that the right units are on the right positions (numerator / denominator).

This equation is dimensionally homogeneous:

z(m) = x(m) + 48(m/s²)

• True

• False

Answer explanation

On the left-hand side, the unit is meters (m).

On the right-hand side, the unit for the 1st term is meters (m). However, the 2nd term has a unit of meters per second squared (m/s²).

Since not all the units are consistent, this equation is NOT dimensionally homogeneous.

This equation is dimensionally homogeneous:

x(m) = y₀(m) + 48(m/ft) v(ft/s) + 0.25a(m/s²) [t (s)]²

• True

• False

Answer explanation

On the left-hand side, the unit is meters (m).

On the right-hand side, the unit for the 1st term, y₀ is meters (m). However, the 2nd term has a unit of meters per second (m/s). The 3rd term has a unit of meters (m).

Since not all the units are consistent, this equation is NOT dimensionally homogeneous.

Convert 1lb to kg.

(Submit your answer in 2 decimal places, without the units.)

Answer explanation

The conversion factor to use for this question is: 1 kg = 2.2046 lb.

Hence, 1 lb = 1 kg ÷ 2.2046 = 0.45 kg