Blocks A and B have a mass MA and MB, respectively. If the coefficient of static friction between A and B and between B and C is us and between the ropes and the pegs D and E us, determine the smallest force F needed to cause motion of block B. Units Used: kN = 103 N Given: ? = 45 deg us = 0.25 MA = 100 kg us = 0.5 %3D %3D MB = 150 kg P = 30 N %3D g = 9.81m/s2 D

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Question 3(a) The non uniform XYZ bar which weighs 155 kg has its centre of gravity G at a distance 4 m from X. This bar rests on a homogeneous crate P. The static coefficient of friction between the bar and the crate is 0.31 while the same between the crate and the floor is 0.22. Determine the mass of the lightest crate P (in kilograms) that can be used to support this non uniform bar in the position shown in Figure 3. The height of the crate is 4.32 m and the length of the bar is 8.59 m. 4 m 3 m - 1 m - Figure 3 Question 3(b) Take an example from everyday life where you can identify the application of the concepts we learn in the "Dry friction" module. Sketch this example and discuss about the effect of friction on that particular scenario. Sketch does not have to be drawn to a scale. (Description should be 250 words or less).

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