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24/07/2018 Engineering Mechanics - - Unit 4 - Week 3 Lectures
https://onlinecourses.nptel.ac.in/noc16_ph02/unit?unit=56&assessment=66 1/7
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Courses » Engineering Mechanics
Unit 4 - Week 3 Lectures
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Week1 Lectures
Week 2 Lectures
Week 3 Lectures
Dry friction I -introduction withan example
Dry friction II - asolved example
Dry friction III -Dry thrustbearing and beltfriction withdemonstration
Dry friction IV -Screw frictionand rollingfriction
Dry friction V:Solvedexamples
Properties ofplane surfaces I- First momentand centroid ofan area
Properties ofplane surfacesII - Centroid ofan area madeby joiningseveral planesurfaces
Properties ofplane surfacesIII - Centroid ofa distributedforce and itsrelation withcentre of gravity
Properties ofplane surfaces
Due on 2016-08-09, 23:59 IST.
1 point1)
1 point2)
Assignment 3The due date for submitting this assignment has passed.
Submitted assignment
A triangular block of mass m is on a horizontal floor, as shown in Fig. 1. The coefficient offriction between the block and the floor is and its inclined side makes an angle with the horizontalside such that . What is the maximum force that can be applied perpendicular to the inclinedside so that the block does not move.
No, the answer is incorrect. Score: 0
Accepted Answers:
Calculate the rolling friction on a tyre assuming that while supporting a weight, it getsflattened on the lower side and the entire support comes from the force arising due to the pressure in thetires and no other deformation takes place. A tyre not supporting any load and another supporting a loadW are shown in the Fig. The tyre has radius R, width b and is filled with air at pressure P. Find (1) thelength ' ' of the rectangular area that is formed on the lower side of the tyre because of the flattening ofthe tyre due to the load, and (2) the rolling friction due to this deformation. Assume that the pressureinside the tyre does not change when it gets flattened.
μ θ
tan(θ) ≥ μ
μmg
sin(θ)−μ cos(θ)
mg
sin(θ)−μ cos(θ)
μmg
sin(θ)−cos(θ)
μmg
cos(θ)−μ sin(θ)
μmg
sin(θ)−μ cos(θ)
a
24/07/2018 Engineering Mechanics - - Unit 4 - Week 3 Lectures
https://onlinecourses.nptel.ac.in/noc16_ph02/unit?unit=56&assessment=66 2/7
Week 4 Lectures
Week 5 Lectures
Week 6 Lectures
Week 7 Lectures
Week 8 Lectures
Week 9 Lectures
Week 10Lectures
Week 11Lectures
Week 12Lectures
Review Problems
IV - solvedexamples ofcalculation offirst momentand centroid ofdistributedforces
Quiz :Assignment 3
1 point3)
1 point4)
No, the answer is incorrect. Score: 0
Accepted Answers:
Find the centroid of the area enclosed between two parabolas(see figure) whose equationsare and
Centroid = (X,Y) = (3, 8) Centroid = (X,Y) = (3, 6) Centroid = (X,Y) = (4, 6) Centroid = (X,Y) = (2, 8) Centroid = (X,Y) = (4, 7)
No, the answer is incorrect. Score: 0
Accepted Answers:Centroid = (X,Y) = (2, 8)
Choose the correct option. The centroid of the shaded region shown in the figure below is at
Centroid = (X, Y) =
Centroid = (X, Y) =
a = , f riction =W
bP
W 2
bPR
a = , f riction =W
bP
W 2
2bPR
a = , f riction =W
bP
W
2bPR
a = , f riction =W
bP
2W
2bPR
a = , f riction =W
bPW 2
2bPR
y = 16 − 4(x − 2)2 y = 4 − (x − 2)2
( , )7
3
5
6
( , )8
5
5
7
24/07/2018 Engineering Mechanics - - Unit 4 - Week 3 Lectures
https://onlinecourses.nptel.ac.in/noc16_ph02/unit?unit=56&assessment=66 3/7
1 point5)
1 point6)
Centroid = (X, Y) =
Centroid = (X, Y) =
No, the answer is incorrect. Score: 0
Accepted Answers:Centroid = (X, Y) =
A disc of radius R has a hole of radius as shown in the figure below.
The distance of the centroid of the remaining disc (shaded portion) from the origin is
No, the answer is incorrect. Score: 0
Accepted Answers:
Mass is on an inclined plane making an angle with the horizontal. The coefficient offriction between the plane and the mass is . It is connected to the rope that goes over a fixed
pulley and holds a block of mass , as shown in Fig. below. The coefficient of frictionbetween the rope and the pulley is . What is the range of mass , so that mass does not slip onthe inclined plane ?
From .
From .
From .
( , )7
6
4
7
( , )7
4
5
3
( , )7
3
5
6
R
2
R
2
R
4
3R
4
2R
5
R
6
R
6
M1 θ
μ1
(tan(θ) ≥ )μ1 M2
μ2 M2 M1
(sin(θ) − cos(θ)) exp(− ( + θ)) to (cos(θ) + sin(θ)) exp( ( + θ))M1 μ1 μ2π
2M1 μ1 μ2
π
2
(sin(θ) − cos(θ)) exp(− ( + θ)) to (sin(θ) + cos(θ)) exp( ( + θ))M1 μ2 μ1π
2M1 μ1 μ2
π
2
(sin(θ) − cos(θ)) exp(− ( + θ)) to (sin(θ) + cos(θ)) exp( ( + θ))M1 μ1 μ2π
2M1 μ1 μ2
π
2
24/07/2018 Engineering Mechanics - - Unit 4 - Week 3 Lectures
https://onlinecourses.nptel.ac.in/noc16_ph02/unit?unit=56&assessment=66 4/7
1 point7)
1 point8)
1 point9)
From .
No, the answer is incorrect. Score: 0
Accepted Answers:From .
Two rigid bodies A and B each weigh 30 N. Body A is kept on the floor and body B is kept onbody A as shown in the Figure. The coefficient of friction between two bodies and between body A andthe floor is 0.1. If a horizontal force of 2 N is applied on body A, the frictional force at the interface ofbody A and body B will be
1 N 0 3 N 2 N
No, the answer is incorrect. Score: 0
Accepted Answers:0
A block of mass M is balanced in place by a string held by a mass of 2 kg at its other end.The string is passing over two pulleys as in Figure. If the coefficient of friction between the string andthe pulleys is 0.18 for one pulley and 0.14 for other, then the maximum value of M that can be balancedby the 2 kg mass is close to
No, the answer is incorrect. Score: 0
Accepted Answers:
A block of weight 500 N is about to move up the plane due to a horizontal force of 800 N(See in the Figure). The coefficient of friction between the contact surface is
(sin(θ) − cos(θ)) exp(− ( + θ)) to (sin(θ) + cos(θ)) exp( (π + θ))M1 μ1 μ2π
2M1 μ1 μ2
(sin(θ) − cos(θ)) exp(− ( + θ)) to (sin(θ) + cos(θ)) exp( ( + θ))M1 μ1 μ2π
2M1 μ1 μ2
π
2
2e3
2e2
2 e√
2e
2 e√
24/07/2018 Engineering Mechanics - - Unit 4 - Week 3 Lectures
https://onlinecourses.nptel.ac.in/noc16_ph02/unit?unit=56&assessment=66 5/7
1 point10)
1 point11)
0.25 0.15 0.53 0.33
No, the answer is incorrect. Score: 0
Accepted Answers:0.53
To hang heavy objects such as flowerpots in a verandah, hooks (See the Figure) are fixed inthe ceiling with the flowerpot hanging from it. The portions of the hook embedded in the wall are ofconical shape (shown in dark color) of lateral length 3 cm and base diameter of 1 cm. Embedded portionof the hook experiences pressure that is zero at the vertex of the cone and increases linearly along itslength to a value of Pa. Find the maximum weight that a hook like this can hold if the coefficientof friction between the embedded portion and the material of the ceiling is 0.4.
715 N 751 N 755 N 757 N
No, the answer is incorrect. Score: 0
Accepted Answers:715 N
A 6-m long massless beam is loaded as shown in the figure. The forces applied by supportsA and B are respectively
5 × 106
24/07/2018 Engineering Mechanics - - Unit 4 - Week 3 Lectures
https://onlinecourses.nptel.ac.in/noc16_ph02/unit?unit=56&assessment=66 6/7
1 point12)
1 point13)
3000 N, 2000 N 2000 N, 3000 N 6750 N, 20250 N 20250 N, 6750 N
No, the answer is incorrect. Score: 0
Accepted Answers:6750 N, 20250 N
A 4-m long beam is loaded as shown in the figure, with the load being 3000 at end Bof the beam. The forces applied by supports A and B are, respectively
0 N, 2000 N 2000 N, 4000 N 1000 N, 2000 N 1500 N, 1500 N
No, the answer is incorrect. Score: 0
Accepted Answers:2000 N, 4000 N
A uniformly loaded propped cantilever beam and its freebody diagram are shown in thefigure. The reactions and and moment M are
Nm−1
R1 R2
24/07/2018 Engineering Mechanics - - Unit 4 - Week 3 Lectures
https://onlinecourses.nptel.ac.in/noc16_ph02/unit?unit=56&assessment=66 7/7
No, the answer is incorrect. Score: 0
Accepted Answers:
= , = ,M =R15ql
8R2
3ql
8
ql2
8
= , = ,M =R13ql
8R2
5ql
8
ql2
8
= , = ,M = 0R15ql
8R2
3ql
8
= , = ,M = 0R13ql
8R2
5ql
8
= , = ,M =R15ql
8R2
3ql
8
ql2
8
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