課程名稱︰普通物理學丙上
課程性質︰森林環境學群、生物材料學群必修，兼通識A7*
課程教師︰李慶德老師
開課學院：同以上
開課系所︰同以上
考試日期（年月日）︰ 102 年 1 月 9 日
考試時限（分鐘）： 100 分鐘
是否需發放獎勵金：是，謝謝您 =)
（如未明確表示，則不予發放）
試題 :
Do any 5 of the exam problems given below!
1. A crate of mass m = 20kg is dropped onto a conveyer belt that moves at a
constant speed of 4m/s, as in Fig.1. The coefficient of kinetic friction
is 0.5.
(a) What is the work done by the friction?
(b) How far does the crate move before reaching its final speed (4m/s)?
(c) When the crate reaches its final speed, how far has the conveyer belt
moved?
Fig.1 is here: http://ppt.cc/bbD7
2. A 1000-kg Subaru GL at rest at a stoplight is struck from the rear by a
1400-kg Pontiac 6000. They couple together and leave skid marks 4m long.
The coefficient of kinetic friction 0.6.
(a) What was their common speed just after the collision?
(b) What was the speed of the Pontiac just prior to the collision?
3. Find the moment of inertia of a circular disk (or solid cylinder) of radius
R and mass M about the following axes:
(a) through the center and perpendicular to the flat surface;
(b) through a point on the disk 1/2R from the center and perpendicular to
the flat surface;
(c) at the rim of the disk and perpendicular to the flat surface.
4. A block of mass m = 0.4 kg is held against, but no attached to a spring of
k = 40N/m which is compressed by 40 cm,as in Fig. 2. When released, the
blocked slides 80 cm up the rough incline before coming to rest. Assume
that the incline makes an angle of 37°with the horizontal. Find:
(a) the kinetic friction coefficient of the rough incline;
(b) the speed of the block just as it leaves the spring.
Fig. 2 is here: http://ppt.cc/8Qux
5. A 15-g bullet strikes and embeds in a 2-kg block suspended at the end of a
1.2-m string. After the collision the string rises to a maximum angle of
22.5°to the vertical.
(a) Find the speed of the bullet.
(b) Evaluate the percentage loss in kinetic energy due to the collision.
_ ^ ^ _
6. A particle of mass m = 2kg has a position r =(2i+3j)m and a velocity v
^ ^ 1 1 _ ^1^
=(-i+5j)m/s, whereas a particle of mass m = 4kg has a position r =(-5i+j)m
_ ^ ^ 2
and a velocity v = (3i-4j) m/s.
2
_
(a) Find the position of the center of mass r of this two-particle system.
CM
_
(b) Find the velocity v of the center of mass.
CM
(c) Evaluate the total linear momentum of this two-particle system.
(d) What is the position of the center of mass 3 s later if there is no
external force.
7. A 70-kg man sits at the rear and of a platform of mass 30kg and length 6 m,
^
which moves initially at 5i m/s over a frictioless surface. At t = 0, he
walks at 2m/s relative to the platform and then sits down at the front end.
During the period he is walking, find
(a) the displacement of the platform;
(b) the displacement of the man;
(c) the displacement of the center of mass.
8. A disk-shaped pulley has mass M = 5kg and radius R = 0.5m. It rotates
freely on a horizontal axis, as in Fig. 3. A block of mass m = 4kg hangs by
a string that is tightly wrapped around the pulley. Assume the system
starts at rest.
(a) Find the angular velocity of the pulley 4 s after the block is released
(b) Find the speed of the block after it has fallen 2 m.
(c) Repeat part(b) by using the conservation of energy.
Fig. 3 is here: http://ppt.cc/dg7K
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