amc110s supdef-tuts #4b

5/25/2018 AMC110S Supdef-tuts #4b

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POLYTECHNIC OF NAMIBIAPrivate Bag 13388, 13 Storch Street, Windhoek, Namibia http://www.polytechnic.edu.na

Tel: +264 (61) 207 9111 Fax: +264 (61) 207 2444

SCHOOL OF ENGINEERINGEmail [email protected]: +264 (61) 207 2514 Fax: +264 (61) 207 2521

Department of Mechanical Engineering

Appl ied Mechanics Statics (AMS 110S)

17thJune 2009

Deferred / Supplementary Test #4b

Force Systems and Equilibrium

Total marks: 35

Note: This Tutorial is to be completed during the tutorial session of two hours,and is to be submit ted at the end of the tutorial session.

IMPORTANT NOTICES:

Write neatly and legibly, as illegible work will not be considered for marks. Ifyou are of the opinion that insufficient information was provided to solve a specificproblem, make realistic assumptions, motivate these and continue solving theproblem based on your assumptions made.

Use F.B.Ds and illust rative diagrams wherever possible.

Clearly show the reference Cartesian axes system used for each question.

Pay attention to units and show the relevant unit in each calculatedanswer.

No marks will be awarded for answers only. Calculations must contain aminimum number of logically sequenced steps followed by an answer.

In cases where two or more different - and undeleted answers are given for the

same item, the right answer will not be considered for marks.

Use gravitational acceleration g = 9.81m/s2.

Answer any 5 questions. All questions carry 7 marks.


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Question 1

The 12-kg solid cylinder is resting in the inclined V-block (Figure Q1). If the coefficientof static friction between the cylinder and the block is 0.45, determine:(a) the friction force F acting on the cylinder at each side before force P is applied.(b) the value of P required to start sliding the cylinder up the incline.

Question 2

A step ladder consisting of two legs pinned together at C is resting on a rough floor asshown in Figure Q2. Will a 72-kg worker be able to change the light bulb if required toclimb to a height of 0.8 m? The uniform legs AC and BC have masses 9 kg and 5.4 kgrespectively. The coefficient of static friction at A and B is 0.48.

Figure Q1 (all dimensions in mm). Figure Q2.

Question 3

Determine the y-coordinate of the centroid of the shaded part in Figure Q3.

Question 4

Determine the area moment of inertia about the centroidal x-axis ( )x

I of the plane area

shown in Figure Q4 using the transfer-of-axis theorem.

Figure Q3. Figure Q4.

Question 5

Calculate the forces in the members BC, CD and CG of the loaded truss composed ofequilateral triangles, each of side length 8 m (Figure Q5).


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Figure Q5.Question 6

A mechanism is designed such that the moments and forces are configured as shown inFigure Q. Represent the resultant of the force system by a single force Rat 01and acouple M. The 100-N, 75-N, 50-N and 25-N forces are in the x-y, x-z, y-zand x-yplanes respectively.

Figure Q6.

Question 7

In the position shown for the log hoist, booms AF and EG are at right angles to oneanother and AF is perpendicular to AB (Figure Q7). If the hoist is handling a 2500 kglog, compute the forces supported by the pins at A and D in this one position due to theweight of the log.

Figure Q7.

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amc110s supdef-tuts #4b

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