Figure shows a two pulley system for hoisting a load of 10 kN. The coefficient of friction between each pulley and the rope is 0.2. The vertical and horizontal distances between the centers of the pulleys are 25m and 16m respectively. The tensions T1 and T2 respectively in kN are <img src="/images/question-image/mining-engineering/mining-machinery/1682418081-M2-6-112-39.PNG" title="Mining Machinery mcq question image" alt="Mining Machinery mcq question image">

The layout of a shaft supported on bearings at A & B is shown. Power is supplied by means of a vertical belt on pulley B which is then transmitted to pulley C carrying a horizontal belt. The angle of wrap is 180’ and coefficient of friction is 0.3. Maximum permissible tension in the rope is 3kN. The radius of pulley at B & C is 300mm and 150mm. Calculate the tension in the rope of pulley C.

A

6778.3N and 7765.3N

B

5948.15N and 2288.75N

C

5468.4N ad 8678.3N

D

None of the listed

The layout of a shaft supported on bearings at A & B is shown. Power is supplied by means of a vertical belt on pulley B which is then transmitted to pulley C carrying a horizontal belt. The angle of wrap is 180’ and coefficient of friction is 0.3. Maximum permissible tension in the rope is 3kN. The radius of pulley at B & C is 300mm and 150mm. If bending moment on point B in horizontal plate is M and in vertical plane is m, then the net bending moment at point B is?

A

M

B

m

C

M+m

D

√M²+m²

The layout of a shaft supported on bearings at A & B is shown. Power is supplied by means of a vertical belt on pulley B which is then transmitted to pulley C carrying a horizontal belt. The angle of wrap is 180’ and coefficient of friction is 0.3. Maximum permissible tension in the rope is 3kN. The radius of pulley at B & C is 300mm and 150mm. If allowable shear stress in the shaft is 70N/mm² and torsional and bending moments are M=1185000N-mm and m=330000N-mm, find the diameter of the shaft.

A

36.8mm

B

39.7mm

C

44.7mm

D

40.3mm

The layout of a shaft supported on bearings at A & B is shown. Power is supplied by means of a vertical belt on pulley B which is then transmitted to pulley C carrying a horizontal belt. The angle of wrap is 180’ and coefficient of friction is 0.3. Maximum permissible tension in the rope is 3kN. The radius of pulley at B & C is 300mm and 150mm. Calculate the torque supplied to the shaft.

A

453.5N-m

B

549.3N-m

C

657.3N-m

D

None of the listed

A two tonne mine car is released from the top of an incline at a height of 3m as shown in the figure. The mine car travels 45m along the inclined track and another 85m along the horizontal track before coming to rest. The specific rolling resistance of the, car in N/tonne is

A

0.226

B

0.326

C

0.526

D

0.126

A block of mass 20 kg lying on a rough horizontal plane is connected by a light string passing over a smooth pulley to another mass 5 kg, which can move freely in the Vertical direction, as shown in the below figure. The tension in the string will ___________ with the increase in coefficient of friction.

A

Increase

B

Decrease

C

Not be effected

D

None of these

A direct rope haulage pulls 8 tubs loaded with coal through an incline of length 500 m having an inclination of 1 in 6. Consider the following additional data.
Capacity of tub = 1.0 tonne.
Tare weight of tub = 500 kg
Hauling speed = 9 km per hour
Coefficient of friction between wheel and rail = $$\frac{1}{{60}}$$
Coefficient of friction between rope and drum = $$\frac{1}{{10}}$$
Mass of rope per meter = 1.5 kg
The minimum power required to haul the tubs in kW is

A

345.50

B

348.60

C

350.10

D

365.50

E

58.86

The ratio of driving tensions for flat belts, neglecting centrifugal tension, is (where T₁ and T₂ = Tensions on the tight and slack sides of belt respectively, $$\mu $$ = Coefficient of friction, between the belt and pulley and $$\theta $$ = Angle of contact)

A

$$\frac{{{{\text{T}}_1}}}{{{{\text{T}}_2}}} = \mu \theta $$

B

$$\log \frac{{{{\text{T}}_1}}}{{{{\text{T}}_2}}} = \mu \theta $$

C

$$\frac{{{{\text{T}}_1}}}{{{{\text{T}}_2}}} = {\text{e}}\mu \theta $$

D

$$\frac{{{{\text{T}}_1}}}{{{{\text{T}}_2}}} = \log \mu \theta $$

The figure shows a shape ABC and its mirror image A₁B₁C₁ across the horizontal axis (X-axis). The coordinate transformation matrix that maps ABC to A₁B₁C₁ is

A

\\

B

\\

A semi-circular disc rests on a horizontal surface with its top flat surface horizontal and circular portion touching down. The coefficient of friction between semi-cricular disc and horizontal surface is i. This disc is to be pulled by a horizontal force applied at one edge and it always remains horizontal. When the disc is about to start moving, its top horizontal force will

A

remain horizontal

B

slant up towards direction of pull

C

slant down towards direction of pull

D

unpredictable