Download MEEN2130 Statics and Dynamics EXAM #2: Solved Questions - Prof. Zhi-Gang Feng and more Exams Mechanical Engineering in PDF only on Docsity!
General Instructions:
1. Answer the questions in the space provided. If you run out of room for an answer, _continue on the back of the page. Please do not remove the staple.
- Calculator and a one-side A4 size formula (no solutions to any problems) sheet are_ allowed, but no other reference material is to be used. You may also request formula and _equations from me.
- The exam has two parts and contains short-answer and long-answer questions. Please_ read the directions of each part before you proceed.
UNT College of Engineering
MEEN2130 Statics and Dynamics EXAM #
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Part I. Enter the answer (including the unit if applicable) for each question into the space provided. It is advised to put your work on the exam sheets so you may get partial credits for having right procedures but incorrect answers.
- For the truss shown below. List all the zero force members by inspection.
Answer: Zero force members:
- For the bridge truss shown below. To determinate the force in member DE, we may apply the method of section by vertically cutting the truss through members DE, DH and IH; and then choose the right part of the truss to apply the equilibrium conditions. We proceed as follows: a. Solve the reaction forces at support G (say Gy ) by considering the equilibrium of the entire truss; b. Vertically cutting the truss through members DE, DH and IH, and draw a FBD of the right part of the truss. c. Apply moment equation ܯ ∑ு ൌ 0 about reference point H to find FDE. What are the values of Gy and FDE? Indicate if FDE is a compression or tension.
Answer: (a) Gy = ( ) (b) F DE = ( )
- A person exerts a horizontal force on the book as shown. The book weight 8 N. If the book is about to slide when the horizontal force is 2 N, what is the coefficient of static friction between the book and the surface?
Answer: (a) ߤ (^) ௦= ( )
6. Block A has a mass of 50 kg and rests on surface. A horizontal force T is applied to the block. What is the minimum coefficient of static friction μs between the block and the surface so that the block won’t tip over before it slides?
Answer: (a) ߤ (^) ௦= ( )
7. For a particle in a rectilinear motion, the v-t graph is shown below. What is the average velocity and average speed between time t= 0 to t=6 s.
Answer: v avg = ( ) ( v sp ) (^) avg = ( )
- A small plane flies horizontally with a speed of 250 ft/sec at an altitude of 400 ft. The pilot drops a package at A. How much time does it take for the package to hit the target? What horizontal lead, L is required so that the package hits the target? (Neglect air resistance between points A and B).
Answer: t s = ( ) L = ( )
- The slotted fork is rotating about O at angular velocity ሶߠ=3 rad/s, which is increasing at angular acceleration ሷߠ= 2 rad/s 2 at ߠ =2π. Determine the magnitudes of velocity and acceleration of the pin A at this instant. The path is defined by the spiral groove ݎൌ 5 ఏ గ.
Answer: (a) v = ( ) (a) a = ( )
Part 2 (40 points): Show all the steps, box your answers.
Choose either problem 2-1A or 2-1B to solve.
2-1A : A very thin bookmark having a width of 1 in. is in the middle of a 12-lb dictionary. If the pages are 8 in by 10 in., determine the force P needed to start to pull the bookmark out. The coefficient of static friction between the bookmark and the paper is 0.7. Assume the pressure on each page and the bookmark is uniform.
2-1B : Determine the force that the smooth roller C exerts on beam AB. Also, what are the horizontal and vertical components of reaction at pin A? Neglect the weight of the frame and roller.
