sample final exam - purdue...

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ME 270 – Summer 2006 Examination No. 1 PROBLEM NO. 3 Given: Below is a Warren Bridge Truss. The total vertical height of the bridge is 10

feet and each triangle has a base of length, L = 8ft. Find: Determine the load carried by members DF, DE, and EG. State whether these

members are in tension or in compression. Note: A free body diagram must accompany each equilibrium equation used in your

analysis.

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ME 270 – Summer 2005 Examination No. 1 PROBLEM NO. 3 Given: The truss shown below supports the applied loads at joints D and E. The

length of each link across the bottom is L = 4ft. and the height of the truss, H = 3 ft.

Find: Determine the load carried by members BC, BD, and CE. State whether these

members are in tension or in compression. Note: A free body diagram must accompany each equilibrium equation used in your

analysis.

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1. Below you will find a figure of a truss attached to the wall by a pin joint at B and a cable that extends from G to A. Make sure you include all the appropriate free body diagrams.

1a. Solve for the forces in the cable AG (6 points).

TAG =

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1b. Determine the forces in links GF, GD, and GC (11 points). 1c. Which of the links that you solved for in part (1b) are in tension (T) and which are in compression (C)? Please circle the correct answer for each (3 points). GF T or C GD T or C GC T or C

FGF = FGD = FGC =

ME 270 - Fall 2004Examination No. 1PROBLEM NO. 3

Given: The truss shown below supports the applied loads at joints A, G and I.

Find: Determine the load carried by members DE, DK and DJ. State whetherthese members are in tension or in compression.Note: A free body diagram must accompany each equilibrium equation usedin your analysis.

3mA B C D E F

O P

G H I J K L

MN

R

S

3m 3m 3m 3m 3m

4m

4m

4m

10 kN 10 kN

20 kN

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ME 270 - Fall 2005 Exam 1 PROBLEM NO. 3 Calculate the forces in links GN, SN, and SM. Indicate whether each one is in tension or compression. You may use any method you wish to solve the problem. (20 points).


ME 270 - Fall 2005Exam 2PROBLEM NO. 1

A massless wedge is used to move Block B (which weights 500 lb.) to the right by applying aforce, P. The coefficient of static friction between the wedge and the wall is µs= 0.20. Thecoefficient of static friction between the block and the floor is µs= 0.30. Frictionless rollers arelocated between the wedge and Block B.

a. Denote the coordinate system and draw the free-body diagrams for the wedge and theblock using the figures provided. (7 points).

b. Determine the forces between Block B and the floor. Show your work. (3 points).c. Determine the force, P, that will begin to move the block to the right. Show your work. (8

points).d. If the rollers are removed (allowing friction between the wedge and the Block) what will

happen to the value for P (circle the correct answer here)? (2 points).

Decrease in P No Change in P Increase in P

P

75°

Block B500 lb

Part a.


ME 270 - Fall 2005Exam 2PROBLEM NO. 2

Below is an image of a pair of ice tongs used to remove ice blocks from the ship’s hold and anidealized pair of tongs raising a 1000 Newton ice block. Please note that the tongs have tosqueeze the ice block in order for the points to penetrate the surface of the ice, thereby enablingthe operator to pick up the block.

• First, if the links that make up the ice tongs are assumed massless, what is the force, P,

required to maintain the system in static equilibrium. (3 points).

• Second, draw a free body diagram of the pin at D and solve for the unknown forces. (6

points).

• Third, draw a free body diagram of the ice block. (2 points).

• Fourth, calculate the forces acting on link ABC. Draw all necessary free body diagrams.

(9 points).

Write the force at A in vector notation.

Write the force at B in vector notation.


3b. The disk below has a triangular cut-out. Calculate the x-component of the centroid relative tothe coordinate system given below. (8 points).

x

y

xc =


3c. A 30-lb. block just begins sliding to the right when a 20-lb. force is applied at the angleshown. Determine the coefficient of friction, µs, between the floor and the block. (6 points).

Force = 20 lbs.

µs =

Block 30 lbs.

30°

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Problem 1 (20 points) 1A. Block A is tied to the wall and block A sits on block B. The coefficient of static friction between them is 0.35. A force P = 200 N is applied to block B. The goal of this problem is to determine the minimum coefficient of friction between block B and the ground required to prevent motion. You may assume mA = 15 kg, and mB = 20 kg. (9 points)


1B. Both wheels of the refrigerator are locked. If H = 1.8 m, b = 0.5 m, and h = 1.2 m, determine the force, P, required to initiate motion of the refrigerator. You may assume the refrigerator weighs 200 N and the coefficient of friction between the wheels and the floor is 0.4. Does it slip or tip? (11 points)


Problem 2 (20 points) The truss shown below is attached by a pin joint at point N and a roller at point K.

2A. Determine the reactions at points K and N. (8 points)


2B. Calculate the forces in links VU, VD, and VC. (12 points)


Problem 3 (20 points) 3A. The plate below has a hole with a radius of 0.2 m in the upper left hand corner. Determine the x-coordinate of the centroid. You must show your work to receive full credit. (10 points)


3B. For what range of weights, W, will the system remain in equilibrium? Assume, θ =

40 degrees. (10 points)

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