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Unformatted text preview: practice 11 ALIBHAI, ZAHID 1 Latest unpenalized work: Apr 8 2007 Sunday 04:00 (after this date you can not make a perfect score). Work cutoff: Apr 8 2007, 4:00 am. Question 1 part 1 of 1 10 points Two weights attached to a uniform beam of mass 38 kg are supported in a horizontal position by a pin and cable as shown in the figure. The acceleration of gravity is 9 . 8 m / s 2 . 23 kg 20 kg 2 . 9 m 8 m 37 38 kg What is the tension in the cable which sup- ports the beam? Answer in units of kN. Question 2 part 1 of 3 10 points A uniform rod pivoted at one end point O is free to swing in a vertical plane in a gravitational field. However, it is held in equilibrium by a force F at its other end. x y F F x F y W R x R R y O Force vectors are drawn to scale. What is the condition for translational equilibrium along the horizontal x direction? 1. F x = 0 2.- R x + F x = 0 3. R x- F x cos = 0 4. R x- F x sin = 0 5. F x cos - R x sin = 0 Question 3 part 2 of 3 10 points What is the condition for translational equilibrium along the vertical y direction? 1. R y + F y- W = 0 2. R y- F y + W = 0 3. R y + F y = 0 4. R y sin + F y sin - W cos = 0 5. W- R y + F y = 0 Question 4 part 3 of 3 10 points Taking the origin (point O ) as the pivot point, what is the condition for rotational equilibrium? 1. F y sin - W 2 sin - F x sin = 0 2. F y cos - W 2 cos - F x sin = 0 3. 2 F y sin - W cos - 2 F x sin = 0 4. W 2- F x cos - F y cos = 0 5. F y cos - W sin + F x sin = 0 Question 5 part 1 of 1 10 points A light string has its ends tied to two walls practice 11 ALIBHAI, ZAHID 2 separated by a distance equal to four-fifth the length L of the string as shown in the figure. A 25 kg mass is suspended from the center of the string, applying a tension in the string. The acceleration of gravity is 9 . 8 m / s 2 . 4 L 5 25 kg L 2 L 2 What is the tension in the two strings of length L 2 tied to the wall? Answer in units of N. Question 6 part 1 of 1 10 points A solid bar of length L has a mass m 1 . The bar is fastened by a pivot at one end to a wall which is at an angle with respect to the horizontal. The bar is held horizontally by a vertical cord that is fastened to the bar at a distance x cord from the wall. A mass m 2 is suspended from the free end of the bar. T m 2 m 1 x cord L Find the tension T in the cord. 1. T = parenleftbigg m 1 + 1 2 m 2 parenrightbiggparenleftbigg L x cord parenrightbigg g cos 2. T = parenleftbigg m 1 + 1 2 m 2 parenrightbiggparenleftbigg L x cord parenrightbigg g 3. T = ( m 1 + m 2 ) parenleftbigg L x cord parenrightbigg parenleftBig g 2 parenrightBig 4. T = parenleftbigg 1 2 m 1 + m 2 parenrightbiggparenleftbigg L x cord parenrightbigg g cos 5. T = ( m 1 + m 2 ) g cos 6. T = parenleftbigg m 1 + 1 2 m 2 parenrightbiggparenleftbigg L x cord parenrightbigg g sin 7. T = parenleftbigg 1 2 m 1 + m 2...
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