課程名稱︰普通物理丙
課程性質︰物理
課程教師︰李慶德
開課學院：生物資源暨農學院
開課系所︰森林資源暨資源學系
考試日期（年月日）︰97年1月16日
考試時限（分鐘）：120分鐘
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
七題選五題作答
1.A crate of mass m is dropped onto a conveyer belt that moves at a constant
speed v.The coefficient of kinetic friction is uk.
(a) What is the work done by friction?
(b) How far does the crate move before reaching its final speed v?
(c) When the crate reaches its final speed v,how far has the conveyer belt
moved?
2.The bob of a simple pedulum of length L=2m has a mass m =2kg and a speed
v=1.2m/s when the string is at 37* to the vertical.
(a) Find the tension in the string at the lowest point in its swing.
(b) What is the tension in the string when the string is at 15* to the
vertical?
3. A force F=24N acts at 60* above the horizontal on a 3-kg block that is
attached to a spring whose stiffiness constant is k =20N/m.Assume uk =0.1
and the system starts at rest with the spring unextended.If the block moves
40cm.
(a)find the work done by F.
(b)find the work done by friction.
(c)find the work done by the spring.
(d)find the final speed of the block.
4.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 is 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?
5.A 15-g bullet strikes and embeds in a 2-kg block suspened 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 75-kg man sits at the rear end of a platform of mass 25kg and length 4m
,which moves initially at 4i m/s over a frictionless surface. At t=0,he
walks at 2 m/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.
7.A disk-shaped pulley has mass M=6kg and radius R = 0.5m.It rotates freely
on a horizontal axis.A block of mass m = 3kg 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 4s after the block is released.
(b) Find the speed of the block after it has fallen 3.6m.
(c) Repeat part (b) by using the conservation of energy.
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