Question 1

A flywheel has a mass of 20 kg and a radius of gyration of 100 mm. Its angular kinetic energy when rotating at 10 rev/s is:

Accepted Answer

A)   2J
B)   20J
C)   790J
D)   7896J C

Question 2

If the moment of inertia of a slender rod of length L and mass m about an axis through its centre is mL2/12, then its moment of inertia about an end is:

Accepted Answer

A)   mL2/12
B)   mL2/3
C)   mL2
D)   13mL2/12 B

Question 3

Decide whether each of these statements is True (T) or False
A flywheel has a moment of inertia of 40 kg m2 about its axis and is at rest when a constant torque of 90 N m is applied. After 15 s:

Accepted Answer

A)   (i)  T (ii)  T
B)   (i)  T (ii)  F
C)   (i)  F (ii)  T
D)   (i)  F (ii)  F A

Question 4

The rotor of a motor is accelerated from rest by a torque of 250 N m. When it has rotated through 10 revolutions, the gain in angular kinetic energy is:

Accepted Answer

A)   2.5kJ
B)   5.0kJ
C)   7.85kJ
D)   15.7kJ

Question 5

The constant torque required to get a wheel of moment of inertia about its axle of 100 kg m2, starting from rest, to rotate at 5 rev/s after 15 s is:

Accepted Answer

A)   14.0 Nm
B)   39.6 Nm
C)   209 Nm
D)   3142 Nm

Exam 15: Angular Dynamics

A flywheel has a mass of 20 kg and a radius of gyration of 100 mm. Its angular kinetic energy when rotating at 10 rev/s is:

If the moment of inertia of a slender rod of length L and mass m about an axis through its centre is mL2/12, then its moment of inertia about an end is:

Decide whether each of these statements is True (T) or False A flywheel has a moment of inertia of 40 kg m2 about its axis and is at rest when a constant torque of 90 N m is applied. After 15 s:

The rotor of a motor is accelerated from rest by a torque of 250 N m. When it has rotated through 10 revolutions, the gain in angular kinetic energy is:

The constant torque required to get a wheel of moment of inertia about its axle of 100 kg m2, starting from rest, to rotate at 5 rev/s after 15 s is: