Machine Kinematics

Laws of Fluid Friction

Question 1
Marks : +2 | -2
Pass Ratio : 100%
A multiple disc clutch has five plates having four pairs of active friction surfaces. If the intensity of pressure is not to exceed 0.127 N/mm2, find the power transmitted at 500 r.p.m. The outer and inner radii of friction surfaces are 125 mm and 75 mm respectively. Assume uniform wear and take coefficient of friction = 0.3.
17.8 kW
18.8 kW
19.8 kW
20.8 kW
Explanation:
n1 + n2 = 5 ; n = 4 ; p = 0.127 N/mm2 ; N = 500 r.p.m. or ω = 2π × 500/60 = 52.4 rad/s ; r1 = 125 mm ; r2 = 75 mm ; μ = 0.3
Question 2
Marks : +2 | -2
Pass Ratio : 100%
The force of friction is dependent of the substances of the bearing surfaces.
True
False
Explanation:
The force of friction is independent of the substances of the bearing surfaces.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
The force of friction is almost dependent of the load.
True
False
Explanation:
The force of friction is almost independent of the load.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
The force of friction is dependent of the velocity of sliding of one body relative to the other body.
True
False
Explanation:
The force of friction is independent of the velocity of sliding of one body relative to the other body.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
The force of friction is inversely proportional to the normal load between the surfaces.
True
False
Explanation:
The force of friction is directly proportional to the normal load between the surfaces.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
A 60 mm diameter shaft running in a bearing carries a load of 2000 N. If the coefficient of friction between the shaft and bearing is 0.03, find the power transmitted when it runs at 1440 r.p.m.
171.4 W
271.4 W
371.4 W
471.4 W
Explanation:
Given : d = 60 mm or r = 30 mm = 0.03 m ; W = 2000 N ; μ = 0.03 ; N = 1440 r.p.m.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
The force of friction depends upon the material of which the contact surfaces are made.
True
False
Explanation:
Following are the laws of solid friction :
Question 8
Marks : +2 | -2
Pass Ratio : 100%
The force of friction is dependent of the area of the contact surface for a given normal load.
True
False
Explanation:
The force of friction is independent of the area of the contact surface for a given normal load.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
A single plate clutch, with both sides effective, has outer and inner diameters 300 mm and 200 mm respectively. The maximum intensity of pressure at any point in the contact surface is not to exceed 0.1 N/mm2. If the coefficient of friction is 0.3, determine the power transmitted by a clutch at a speed 2500 r.p.m.
61.693 kW
71.693 kW
81.693 kW
91.693 kW
Explanation:
Given : d1 = 300 mm or r1 = 150 mm ; d2 = 200 mm or r2 = 100 mm ; p = 0.1 N/mm2 ; μ = 0.3 ; N = 2500 r.p.m. or ω = 2π × 2500/60 = 261.8 rad/s
Question 10
Marks : +2 | -2
Pass Ratio : 100%
The force of friction is _____________ for different lubricants.
same
different
zero
none of the mentioned
Explanation:
The force of friction is different for different lubricants.