Engineering Physics Homework

Question 1

Define moment of inertia.

Answer 1

The moment of inertia (I) is a measure of an object’s resistance to rotational acceleration about an axis.

Question 2

What is the equation to calculate the moment of inertia of a point mass?

Answer 2

I=mr^2

Question 3

What two factors affect an object’s moment of inertia?

Answer 3

Its total mass and how that mass is distributed about the axis of rotation.

Question 4

What is the equation for rotational kinetic energy?

Answer 4

Ek = 1/2 Iω^2

Question 5

Write down the equations for angular velocity, angular displacement, and angular acceleration

Answer 5

ω=Δθ/Δt
​
α=Δω/Δt
​

Question 6

Write down the two equations used to calculate torque.

Answer 6

T=Fr

T=Iα

Question 7

Write down the equations for work done and power for a rotating body.

Answer 7

W=Tθ

P=Tω

Question 8

How do we account for frictional torque in rotating machines?

Answer 8

T=Iα

frictional torque is minimised by lubrication, superconducting bearings, or vacuums.

Question 9

What is a flywheel?

Answer 9

A heavy rotating disc with a large moment of inertia that stores rotational kinetic energy.

Question 10

What factors affect the energy storage capacity of a flywheel?

Answer 10

Mass, angular speed, friction, and mass distribution (more at edges = higher I).

Question 11

How are flywheels used to store energy in systems?

Answer 11

convert input torque into rotational kinetic energy for use during power fluctuations

Question 12

Write down the law of conservation of angular momentum and its equation.

Answer 12

When no external torque acts, angular momentum remains constant.
I1ω1=I2ω2
​

Question 13

Define angular impulse using an equatio

Answer 13

Angular impulse=TΔt=Δ(Iω)

Question 14

What equation describes the first law of thermodynamics?

Answer 14

Q=ΔU+W

Question 15

What is a non-flow process

Answer 15

A thermodynamic change in a closed system where no gas enters or leaves.

Question 16

Write down the ideal gas equation for a general non-flow process

Answer 16

pV=nRT

Question 17

What is an isothermal change? How can it be approximated in real processes?

Answer 17

Temperature remains constant ΔU=0

approximated by slow processes with good heat conduction.

Question 18

What is an adiabatic change? How can it be approximated in real processes?

Answer 18

No heat transfer Q=0

approximated by rapid processes in well-insulated systems.

Question 19

Write down the ideal gas law for an isothermal process and the first law for it.

Answer 19

pV=constant;

Q=W

Question 20

Write down the ideal gas law for an adiabatic process and the first law for it.

Answer 20

pV^γ = constant

ΔU=−W

Question 21

Write down the ideal gas law for a constant-pressure process and the first law for it.

Answer 21

V1 / T1 = V2 / T2
Q=ΔU+W=ΔU+pΔV

Question 22

Write down the ideal gas law for a constant-volume process and the first law for it.

Answer 22

p1/T1 = p2 / T2

Q=ΔU

Question 23

Define an isotherm.

Answer 23

A line on a p–V diagram showing constant temperature.

Question 24

How to calculate work done on p–V diagrams for each process?

Answer 24

Work = area under the curve; no area (and thus no work) for constant volume.

Question 25

What happens during each stroke of a four-stroke petrol cycle?

Answer 25

Induction → Compression → Expansion → Exhaust.

Question 26

What happens during each stroke of a four-stroke diesel cycle?

Answer 26

Induction (air only) → Compression (air heats) → Expansion (fuel ignites) → Exhaust.

Question 27

What four assumptions are made for theoretical indicator diagrams?

Answer 27

1) Same pure air used throughout (γ = 1.4) 2) Instant pressure/temperature change 3) No friction 4) External heat source

Question 28

How do real and theoretical indicator diagrams compare?

Answer 28

Real diagrams have rounded edges, lower peaks, smaller area due to friction, incomplete combustion, and valve timing.