课程名称︰普通物理学甲上 课程性质︰系内必带 课程教师︰王立民 开课学院：工学院 开课系所︰土木工程学系 考试日期（年月日）︰98/12/17 考试时限（分钟）：110min 是否需发放奖励金：是，谢谢 （如未明确表示，则不予发放） 试题 : 普通物理平时考(CH10,11) 试题附图：http://i814.photobucket.com/albums/zz65/kenyang0531/Untitled-3.jpg 1. Figure 1 shows an arrangement of 15 identical solid spheres that have been glued together in a rod-like shape of length L = 3.0 m and (total) mass M = 150.0 mg. The arrangement can rotate about a perpendicular axis through its central disk point O. (a) What is the rotational inertia of the arrangement about the axis?(10%) (b) If we approximated the arrangement as being a uniform rod of mass M an length L, what percentage error would we make in using the formula in Table 10-2e to calculate the rotational inertia?(5%) (c) If there are N (N is odd) identical solid spheres, please re-estimate the inertia in (a).(10%) (d) Show that if N→∞, the inertia is equal to the result in Table 10-2e. [Hint:2^2+4^2+....+(N-1)^2=N(N^2-1)/6] 2.In Fig. 2, the pully which can be regarded as a disk, is mounted in horizontal frictionless bearings with a radius of 20.0 cm and mass of 0.2 kg, and the inclined plane are frictionless. Block A has a mass of 1.0 kg, block B has a mass of 2.0 kg, and angle θ is 30°. When released form rest, (without the cord clipping on the pully) (a) What is the magnitude of the block's acceleration? What is the tension in the cord that supports (b) Block A and (c) the Block B? (d) What is the magnitude of the pulley's angular acceleration?(20%) 3.In Fig. 3, a solid brass ball of mass 0.280 g will roll smoothly along a loop -the-loop track when released from rest along the straight section. The circular loop has radius R = 14.0 cm, and the ball has radius r = 2.0 cm. (a) What is h if the ball is on the verge of leaving the track when it reaches the top of the loop? If the ball is released at height h = 84.0 cm, what are the (b) magnitude of the normal force from the loop acting on tha ball at the point Q? and (c) the magnitude of the normal force from the loop acting on the ball at the lowest point P?(15%) 4.In Fig.4, a small 50 g disk with a radius of 1 cm goes smooth rolling motion down a friction surface through height h = 20 cm and then sticks to a uniform rod of mass 100 g and length 40 cm. The rod pivots about point O through angle θ before momentarily stopping. (a) Find the speed of the ball at the lowest point bofore the collision, and (b) find θ.(20%) 5.Proof the result : I=M(a^2+b^2)/12 as shown in Table 10-2 i.(15%) [Hint:Using I=ML^2/12 for a uniform rod with a perpendicular rotation axis through it's center.] --

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