# Machine Dynamics Questions and Answers – Stability of a Four Wheel drive Moving in a Curved Path

This set of Machine Dynamics Multiple Choice Questions & Answers (MCQs) focuses on “Stability of a Four Wheel drive Moving in a Curved Path”.

1. Which of the following relation is correct regarding the net gyroscope couple C acting on a four wheel vehicle?
a) ωw.ωp (4 Iw ± G.Ie)2
b) ωw.ωp (4 Iw* G.Ie)
c) ωw.ωp (4 Iw ± G.Ie)
d) ωw2(4 Iw ± G.Ie)

Explanation: When a four wheeled vehicle undergoes a motion along a curved path, the gyroscope couple acts on the vehicle. This effect depends on angular velocities of precession & wheels and moment of inertia of wheels and rotating parts of engine.

2. The positive sign is used to determine the gyroscope couple in which of the following cases?
a) When the wheels and rotating parts of the engine rotate in the same direction
b) When the wheels and rotating parts of the engine rotate in the opposite direction
c) When the precession is clockwise
d) When the precession is anticlockwise

Explanation: The positive sign is used when the wheels and rotating parts of the engine rotate in the same direction. If the rotating parts of the engine revolve in opposite direction, then negative sign is used.

3. If the net gyroscope couple is negative then which of the following is true?
a) The reaction will be vertically downwards on the outer wheels and vertically upwards on the inner wheels
b) The reaction will be vertically upwards on the outer wheels and vertically downwards on the inner wheels
c) The reaction will be vertically downwards on the outer wheels and vertically downwards on the inner wheels
d) The reaction will be vertically upwards on the outer wheels and vertically upwards on the inner wheels

Explanation: A negative gyroscope couple would result in opposite direction of the reaction from the ground in the wheels of the vehicle.

4. The relation between overturning couple and height of centre of gravity is given by_______
a) Co = Fcxh
b) Co = Mv2xh/R
c) Co = Mv2 * (h/R)2
d) Co = Mv2 * h/R2

Explanation: Centrifugal force is given by : Fc = (Mv2)/R and the overturning couple is the cross product of h and Fc.

5. In order to maintain contact between inner wheel and ground the sum of vertical reactions at each of the outer and inner wheels should be less than______
a) W
b) W/2
c) W/4
d) W/3

Explanation: The total vertical reaction at each of the inner wheel will be negative if the sum of vertical reactions at each of the outer and inner wheels is less than W/2.

6. Let x be the track width of the vehicle, then which of the following expression is correct for vertical reaction Q at the two outer or inner wheels?
a) Q = (Mv2. h)/ (R.x)
b) Q = (Mv2)/ R
c) Q = Mv2. x/ (R.h)
d) Q = (Mv2)/ (x)

Explanation: Centrifugal force is given by : Fc = (Mv2)/R and the overturning couple is the cross product of h and Fc, and Q=Co/x. Therefore Q = (Mv2.h)/ (R .x)

7. The overturning couple acting on the four wheeler vehicle is balanced by which of the following forces?
a) Centripetal force
b) Centrifugal force
c) Vertical reactions
d) Horizontal reactions

Explanation: Since the overturning couple tends to overturn the vehicle upside down about a horizontal plane, the vertical reactions provide stability and helps in preventing the overturn.

8. Overturning couple is independent of the track width.
a) False
b) True

Explanation: The overturning is the cross product of height of center of gravity and the centrifugal force. Since the centrifugal force does not depend on the track width, the overturning couple is independent of the track width.

9. Assuming that a vehicle is taking a left turn, The gyroscopic couple acting on the vehicle has a tendency to _____ the inner wheels and ____ the outer wheels.
a) Press, Lift
b) Lift, Press
c) Press, Press
d) Lift, Lift

Explanation: While taking a left turn, a four wheel vehicle undergoes the action of a gyroscopic couple which has an effect on inner and outer wheels. This effect results in lifting of inner wheel and pressing of the outer wheel. This prevents the overturning of vehicle.

10. Which of the following factor is not responsible for the stability of a 4 wheel vehicle while negotiating a turn?
a) Pitching
b) Reaction due to weight of Vehicle
c) Effect of Gyroscopic couple due to Wheel
d) Effect of Gyroscopic Couple due to Engine

Explanation: Pitching effect is not pronounced in four wheel vehicles and thus has a negligible effect on the stability of the vehicle while the other 3 factors play a vital role in preventing the overturning of the vehicle.

Sanfoundry Global Education & Learning Series – Machine Dynamics.

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