## 02.4. dynamics

Question Number. 1. A good refrigerant has a.

Option A. low condensation temperature and high condensation pressure.

Option B. low condensation temperature and low condensation pressure.

Option C. high condensation temperature and low condensation pressure.

Correct Answer is. high condensation temperature and low condensation pressure.

Explanation. NIL.

Question Number. 2. What is the momentum of a ball of mass 2 grams and has a velocity of 10cm/s?.

Option A. 5 kg.m/s.

Option B. 20 kg.m/s.

Option C. 0.0002 kg.m/s.

Correct Answer is. 0.0002 kg.m/s.

Explanation. Momentum = mass * velocity. But first convert the numbers to SI. (2 grammes = 2/1000 kg. 10cm = 10/1000 Metres).

Question Number. 3. A gyroscope suffers from apparent wander. This is due to.

Option A. friction on the gimbals and bearings.

Option B. the earth's rotation.

Option C. the aircraft flying along a north/south track.

Correct Answer is. the earth's rotation.

Explanation. Real wander is physical movement from friction in bearings. Apparent wander is due to effect of earth's rotation.

Question Number. 4. The SI unit of momentum is the.

Option A. metre squared (m2).

Option B. kilogram metre per second.

Option C. kilogram / metre (kg/m).

Correct Answer is. kilogram metre per second.

Explanation. Momentum = mass * velocity. So units are kg m/s.

Question Number. 5. Precession in a gyro is.

Option A. proportional to the magnitude of the torque applied.

Option B. proportional to the square of the magnitude of the torque applied.

Option C. inversely proportional to the magnitude of the torques applied.

Correct Answer is. proportional to the magnitude of the torque applied.

Explanation. NIL.

Question Number. 6. A gyro with a fixed point free to rotate in three axis is.

Option A. a tied gyro.

Option B. a space gyro.

Option C. an earth gyro.

Correct Answer is. a tied gyro.

Explanation. If the gyro is fixed to one point, it is a tied gyro. (An earth gyro is 'tied' specifically to an earth reference point).

Question Number. 7. What type of friction requires the greatest force to overcome it?.

Option A. Dynamic friction.

Option B. Static friction.

Option C. Rolling friction.

Correct Answer is. Static friction.

Explanation. Static friction (sometimes called 'stiction') is the greatest friction. Followed by Dynamic and Rolling respectively.

Question Number. 8. If a gyro is constrained to an external reference and has three degrees of freedom it is.

Option A. a tied gyro.

Option B. an earth gyro.

Option C. a space gyro.

Correct Answer is. a tied gyro.

Explanation. A tied gyro has one axis fixed to a point (in space or on earth). An earth gyro is a tied gyro but with one axis specifically fixed to a reference on earth.

Question Number. 9. The point at which an applied force overcomes friction and an object begins to move is the co-efficient of.

Option A. limiting friction.

Option B. static friction.

Option C. kinetic friction.

Correct Answer is. limiting friction.

Explanation. NIL.

Question Number. 10. The amount a gyro precesses when a torque is applied is.

Option A. proportional to the torque.

Option B. inversely proportional to the torque.

Option C. proportional to the square of the torque.

Correct Answer is. proportional to the torque.

Explanation. NIL.

Question Number. 11. The gyroscopic principle is based upon.

Option A. Newton’s 3rd Law.

Option B. Newton’s 2nd Law.

Option C. Newton’s 1st Law.

Correct Answer is. Newton’s 1st Law.

Explanation. Newton's First Law is also called the 'Inertia Law'.

Question Number. 12. A mass of 20kg produces a momentum of 300kgm/s. What is the Kinetic energy?.

Option A. 3250 Joules.

Option B. 2250 Joules.

Option C. 0.25 Kilojoules.

Correct Answer is. 2250 Joules.

Explanation. Momentum = MV, 300 = 20V, V = 15. KE = 1/2MV2 = 1/2*20*15*15 = 2250J.

Question Number. 13. A motorcycle of mass 400kg is moving at a velocity of 8m/s. Calculate its momentum.

Option A. 3200 kgm/s.

Option B. 50 kgm/s.

Option C. 320 kgm/s.

Correct Answer is. 3200 kgm/s.

Explanation. Momentum = mass * velocity.

Question Number. 14. If the speed of a gyro is increased, the force required to precess the gyro is.

Option A. increased.

Option B. remains the same.

Option C. decreased.

Correct Answer is. increased.

Explanation. Rigidity increases with RPM.

Option A. low condensation temperature and high condensation pressure.

Option B. low condensation temperature and low condensation pressure.

Option C. high condensation temperature and low condensation pressure.

Correct Answer is. high condensation temperature and low condensation pressure.

Explanation. NIL.

Question Number. 2. What is the momentum of a ball of mass 2 grams and has a velocity of 10cm/s?.

Option A. 5 kg.m/s.

Option B. 20 kg.m/s.

Option C. 0.0002 kg.m/s.

Correct Answer is. 0.0002 kg.m/s.

Explanation. Momentum = mass * velocity. But first convert the numbers to SI. (2 grammes = 2/1000 kg. 10cm = 10/1000 Metres).

Question Number. 3. A gyroscope suffers from apparent wander. This is due to.

Option A. friction on the gimbals and bearings.

Option B. the earth's rotation.

Option C. the aircraft flying along a north/south track.

Correct Answer is. the earth's rotation.

Explanation. Real wander is physical movement from friction in bearings. Apparent wander is due to effect of earth's rotation.

Question Number. 4. The SI unit of momentum is the.

Option A. metre squared (m2).

Option B. kilogram metre per second.

Option C. kilogram / metre (kg/m).

Correct Answer is. kilogram metre per second.

Explanation. Momentum = mass * velocity. So units are kg m/s.

Question Number. 5. Precession in a gyro is.

Option A. proportional to the magnitude of the torque applied.

Option B. proportional to the square of the magnitude of the torque applied.

Option C. inversely proportional to the magnitude of the torques applied.

Correct Answer is. proportional to the magnitude of the torque applied.

Explanation. NIL.

Question Number. 6. A gyro with a fixed point free to rotate in three axis is.

Option A. a tied gyro.

Option B. a space gyro.

Option C. an earth gyro.

Correct Answer is. a tied gyro.

Explanation. If the gyro is fixed to one point, it is a tied gyro. (An earth gyro is 'tied' specifically to an earth reference point).

Question Number. 7. What type of friction requires the greatest force to overcome it?.

Option A. Dynamic friction.

Option B. Static friction.

Option C. Rolling friction.

Correct Answer is. Static friction.

Explanation. Static friction (sometimes called 'stiction') is the greatest friction. Followed by Dynamic and Rolling respectively.

Question Number. 8. If a gyro is constrained to an external reference and has three degrees of freedom it is.

Option A. a tied gyro.

Option B. an earth gyro.

Option C. a space gyro.

Correct Answer is. a tied gyro.

Explanation. A tied gyro has one axis fixed to a point (in space or on earth). An earth gyro is a tied gyro but with one axis specifically fixed to a reference on earth.

Question Number. 9. The point at which an applied force overcomes friction and an object begins to move is the co-efficient of.

Option A. limiting friction.

Option B. static friction.

Option C. kinetic friction.

Correct Answer is. limiting friction.

Explanation. NIL.

Question Number. 10. The amount a gyro precesses when a torque is applied is.

Option A. proportional to the torque.

Option B. inversely proportional to the torque.

Option C. proportional to the square of the torque.

Correct Answer is. proportional to the torque.

Explanation. NIL.

Question Number. 11. The gyroscopic principle is based upon.

Option A. Newton’s 3rd Law.

Option B. Newton’s 2nd Law.

Option C. Newton’s 1st Law.

Correct Answer is. Newton’s 1st Law.

Explanation. Newton's First Law is also called the 'Inertia Law'.

Question Number. 12. A mass of 20kg produces a momentum of 300kgm/s. What is the Kinetic energy?.

Option A. 3250 Joules.

Option B. 2250 Joules.

Option C. 0.25 Kilojoules.

Correct Answer is. 2250 Joules.

Explanation. Momentum = MV, 300 = 20V, V = 15. KE = 1/2MV2 = 1/2*20*15*15 = 2250J.

Question Number. 13. A motorcycle of mass 400kg is moving at a velocity of 8m/s. Calculate its momentum.

Option A. 3200 kgm/s.

Option B. 50 kgm/s.

Option C. 320 kgm/s.

Correct Answer is. 3200 kgm/s.

Explanation. Momentum = mass * velocity.

Question Number. 14. If the speed of a gyro is increased, the force required to precess the gyro is.

Option A. increased.

Option B. remains the same.

Option C. decreased.

Correct Answer is. increased.

Explanation. Rigidity increases with RPM.