1. For a porter governor, the following data is given:
Mass of each ball = 5kg
Mass on the sleeve = 20Kg
Length of each arm = 20cm
Ball path at life = 12 cm
Path at maximum speed = 16 cm, If there is a friction at the sleeve of 10 N, find the coefficient of insensitiveness.
a) 4%
b) 6%
c) 5%
d) 7%
Explanation: We know that coefficient of insensitiveness is given by
F/(m+M)g
= 10/(5 + 20)9.81 = 4%
2. With increase in friction, coefficient of insensitiveness increases.
a) True
b) False
Explanation: Coefficient of insensitiveness is directly proportional to the friction at the sleeve and inversely proportional to the sum of masses of ball and the weight at sleeve, hence increase in friction results in increase in coefficient of insensitiveness.
3. The brakes commonly used in railway trains is
a) shoe brake
b) band brake
c) band and block brake
d) internal expanding brake
Explanation: A single block or shoe brake consists of a block or shoe which is pressed against the rim of a revolving brake wheel drum. The block is made of a softer material than the rim of the wheel. This type of a brake is commonly used on railway trains and tram cars.
4. The brake commonly used in motor cars is
a) shoe brake
b) band brake
c) band and block brake
d) internal expanding brake
Explanation: The internal expanding type of brake is commonly used in motor cars and light trucks.
5. When brakes are applied to all the four wheels of a moving car, the distance travelled by the car before it is brought to rest, will be
a) maximum
b) minimum
c) equal
d) none of the mentioned
Explanation: When the brakes are applied to all the four wheels, the braking distance (i.e. the distance in which the vehicle is brought to rest after applying the brakes) will be the least. It is due to this reason that the brakes are applied to all the four wheels.
6. Which of the following is an absorption type dynamometer ?
a) prony brake dynamometer
b) epicyclic-train dynamometer
c) torsion dynamometer
d) none of the mentioned
Explanation: Absorption type dynamometers are
1. Prony brake dynamometer,
2. Rope brake dynamometer.
7. The transmission type of dynamometer is a
a) prony brake dynamometer
b) epicyclic-train dynamometer
c) torsion dynamometer
d) none of the mentioned
Explanation: Transmission type dynamometers are
1. Epicyclic-train dynamometer,
2. Belt transmission dynamometer,
3. Torsion dynamometer.
8. The material used for the brake lining should have
a) It should have low wear rate.
b) It should have high heat resistance.
c) It should have high heat dissipation capacity.
d) All of the mentioned
Explanation: The material used for the brake lining should have the following characteristics:
1. It should have high coefficient of friction with minimum fading.
2. It should have low wear rate.
3. It should have high heat resistance.
4. It should have high heat dissipation capacity.
5. It should have adequate mechanical strength.
6. It should not be affected by moisture and oil.
9. The capacity of a brake depends upon
a) The unit pressure between the braking surfaces,
b) The coefficient of friction between the braking surfaces,
c) The peripheral velocity of the brake drum
d) All of the mentioned
Explanation: The capacity of a brake depends upon the following factors :
1. The unit pressure between the braking surfaces,
2. The coefficient of friction between the braking surfaces,
3. The peripheral velocity of the brake drum,
4. The projected area of the friction surfaces, and
5. The ability of the brake to dissipate heat equivalent to the energy being absorbed.
10. For high speed engines, the cam follower should move with
a) uniform velocity
b) simple harmonic motion
c) uniform acceleration and retardation
d) cyclodial motion
Explanation: For high speed engines, the cam follower should move with cyclodial motion. For S.H.M. cam, the acceleration of the follower at the ends of the stroke and aimed stroke respectively, is maximum and zero.