Solved University Question Papers December-2019

Solved University Question Papers

December-2019 

Engineering Mechanics

Semester-II/III (Mech./Auto. / Prod. / Civil)

Regulation 2017

[Time: Three Hours] [Maximum Marks: 100]

AU Solved Paper (90283)

Answer ALL Questions

PART A - (10 x 2 = 20 Marks)

Q.1

State Newton's first law of motion. 

(Refer Q.4 of Chapter - 1)

Q.2

Find out the force system on which the following belong to:

i) Forces acting on a moving bus

ii) Forces on a rod resting against a wall.

Ans.:

Co-planar and non-concurrent force system.

ii) Non-coplanar and non-concurrent force system.

Q.3

State the concept of equilibrium of connected bodies. 

(Refer Two Marks Q.19 of Chapter - 2)

Q.4

Find the moment of 100 N force acting at B about point A as shown in Fig. 1.

Ans.:

Q.5

What are principal axes? What are principal axes of inertia of an area ? 

(Not in New Syllabus)

Q.6

When a lamina possesses axes of symmetry, what does it indicate ?

Ans.:

When a lamina possesses axes of symmetry, the CG lies on that axis.

Q.7

Indicate the concept involved the following games. 

i) Billiards

ii) Boxing.

Ans.:

i) Billiards: In case of billiards concept of impact (collision between balls) is used.

ii) Boxing : In case of boxing velocity, energy and momentum concept is used.

Q.8

Distinguish power and energy.

Ans.:

Capacity to do work is known as energy (unit is N-m) and rate of change of energy is known as power (unit is watts).

Q.9

What is rolling resistance? 

[Refer Two Marks Q.14 of Chapter 8]

Q.10

How ladder friction varies from a wadge friction?

Ans.:

In case of ladder friction there is friction between ladder and wall or ladder and floor.

In case of wedge friction there is friction between two wedges, wall and floor. 

PART B - (5 × 13 = 65 Marks)

Q.11 

a) A roller of weight 10 kN rests on a smooth horizontal floor and is connected to the floor by the bar AC as shown in Fig. 2. Determine the force in the bar AC and reaction from floor, if the roller is subjected to a horizontal force of 5 kN and an inclined force of 7 kN as shown in the Fig. 2 

(Refer example 3.10.23)

OR

b) A rope AB, 4.5 m long is connected at two points A and B at the same level 4 m apart. A load of 1500 N is suspended from a point C on the rope 1.5 m from A as shown in Fig. 3. What load connected at a point D on the rope. 1 m from B will be necessary to keep the position CD level? 

(Refer example 4.6.45)

Q.12 

a) The system of forces acting on a bell crank is shown in Fig. 4. Determine the magnitude, direction and the point of application of the resultant.

(Refer example 3.10.24)

OR

b) Determine the reactions at A and B of the over-hanging beam shown in Fig. 5. 

(Refer example 4.6.46)

Q.13 

a) From a semicircular lamina of radius r, a circular lamina of radius (r/2) is removed as sown in Fig. 6. Find the position of centre of gravity of the remainder. 

(Refer example 5.3.27)

 OR

b) Find the moment of inertia of a hollow rectangular plane shown in Fig. 7 about x-axis and y-axis through the centroid. 

(Refer example 6.6.22)

Q.14 

a) An inset crawls at a constant speed u along the spoke of a bicycle wheel (Fig. 8), which is rotating with a constant angular velocity w. Find the acceleration of inset in radial and perpendicular directions to the spoke.

(Not in new syllabus)

OR

b) A package of mass 60 kg, moving with velocity 2.5 m/s on a surface of friction μk hits a spring of constant 20 kN/m and compressed initially by 12.0 cm. If block compresses the spring further to the maximum of 4.0 cm and the block is initially 60 cm away from end of spring, determine μk and velocity of block when it just starts pressing spring (see Fig. 9). 

(Refer example 9.3.15)

Q.15 

a) A body weighing 700 N rests on a rough horizontal surface. If μs = 0.4,

a) Will the body move if a pull of 200 N is applied to it at 30° to the horizontal ? 

b) If this force is increased to 300 N, investigate the condition of the body. 

(Refer similar example 8.6.3)

OR

b) i) Explain absolute and relative velocity of particles of rigid body in plane motion. 

(Not in new syllabus)

ii) Explain instantaneous centre of zero velocity in plane motion.

(Not in new syllabus)

PART C - (1 × 15= 15 Marks)

Q.16 

a) Find the moment of inertia of circular plate of radius R and thickness t about its centroidal axis. 

(Refer section 7.3)

OR

b) A pole is held in place by three cables. If the force of each cable acting on the pole is shown, determine the position (x, y, 0) for fixing cable DC so that the resultant force exerted on the pole is directed along its axis. 

(Refer example 2.12.34)