课程名称︰普通物理学乙
课程性质︰医学系必修
课程教师︰董成渊
开课学院：理学院
开课系所︰物理系
考试日期（年月日）︰2020/10/14
考试时限（分钟）：50
试题 :
1. A ball with an intial speed of 15 m/s slows down to 5 m/s in 25m. Find：
(a) the frictional force on it;
(b) the coefficient of friction.
2. At t=0 a flywheel is rotating at 50 rpm. A motor gives it a constant
acceleration of 0.5 rad/s^2 until it reaches 100rpm. The motor is then
disconnected. Find：
(a) How much time does it take to accelerate to 100 rpm?
(b) How many revolutions are completed?
3. An Eskimo kid slides on an icy(frictionless) hemispherical igloo of radius
R. She starts with a negligible speed at the top.
(a) At what angle to the vertical does she lose contact with the surface?
(b) If there were friction , would contact be lost at a higher or lower
point?
4. The pendulum of a grandfather clock consists of mass 1.2 kg and length 60
cm. At its end is a disk of radius 5 cm and mass 0.4 kg. It is released
when the rod is 30 degrees to the vertical.
( The moment of inertia for a rod to the axis vertical to its center of mass
is 1/12 mL^2 ; the moment of inertia for a disk is 1/2 mL^2 )
(a) What is the moment of inertia about the axis at the top of the rod?
(b) What is the speed of the lowest point when the rod is vertical?