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VU22475 Apply Scientific Principles to Engineering Problems Calculate the maximum deceleration of a car that is heading down a 8 slope (one that makes an angle of 8 with the horizontal). You may assume that the weight of the car is evenly distributed on all four tires and that the coefficient of static friction is involved - that is, the tires are not allowed to slip during the deceleration. The acceleration due to gravity is 10 m/s2 Q1). Calculate for the car: On dry concrete (u a). 1.0) b). On wet concrete (u 0.7) On ice, assuming that ps 0.100 c). 4+4+4 marks Q2). Consider the 72.0 kg mountain climber in Figure 1.0 below (g 10 m/s2): Find the tension in the rope and the force that the mountain climber must exert with her feet on the vertical rock face to remain stationary. Assume that the force is exerted parallel to her legs. Also,, assume negligible force exerted by her arms. a). What is the minimum coefficient of friction between her shoes and the cliff ? b). 31 15 Figure 1.0 6+4 marks vu22475 Apply Scientific Principles to Engineering Problems Consider the 60.0 kg ice skater in Figure 1.2 below (g 10m/s) Q3). Find the direction and magnitude of Fst, the total force exerted on her by the others, given that the magnitudes of F1 and F2 are 28.2 N and 16.8 N, respectively. a). What is her initial acceleration if she is initially stationary and wearing steel-bladed skates that point in the direction of Fe? b). What is her acceleration assuming she is already moving in the direction of Fot ? c). Remember that friction always acts in the direction opposite that of motion or attempted motion between surfaces in contact with each other Note: F F Free-body diagram Figure 1.2 2+4+2 marks A 86.0 kg person is being pulled away from a burning building as shown in Figure 1.3 below (g 10 m/s2). Calculate the tension in the two ropes if the person is momentarily motionless. Include a free body diagram in your solution Q4). T Figure 1.3 8 marks Creation date eview dete 24/03/20 Veion 201e1 03/19 OMelboume Polytechnic 2017 Page 3 of 4 o WelgHt 5% TOLal MialKs 46 Coefficients of Static and Kinetic Friction System Static friction us Kinetic friction Rubber on dry concrete 1.0 0.7 Rubber on wet concrete Wood on wood Waxed wood 0.7 0.5 0.5 0.3 on wet snow 0.14 0.1 Metal on wood 0.5 0.3 Steel on steel (dry) 0.6 0.3 Steel on steel (oiled) 0.05 0.03 Teflon on steel 0.04 0.04 Bone lubricated by synovial fluid 0.016 0.015 Shoes on wood 0.9 0.7 Shoes on ice Ice on ice Steel on ice 0.1 0.05 0.1 0.03 0.4 0.02 0.04 e: 24/03/19 : 24/03/20 19.1 O Melbourne Polytechnic 2017 Page 1 of 4

Answer 1

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