Deck 15: Angular Dynamics

Question 1

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:

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

Answer 1

B

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:

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

Answer 2

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:

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

Answer 3

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:

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

Question 5

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:

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