Physics 201 MWF10:20 Fall 1994 (Ford)
Exam II Chapts. 6-8 in SZY College Physics
Show all your work. Partial credit will be given if earned. Write your
answers in the blanks provided.
(20 pts) 1. A small block of mass 0.30 kg is attached to a vertical rod
by two strings. One string makes an angle of 37° with the rod and the
other string is horizontal. The system rotates and makes 2.0 rev each second.
The block moves in a horizontal circle of radius 0.15 m.
a) What is the period of rotation of the block, the time to make one revolution?
Ans. __________________
b) What is the speed v of the block?
Ans. _________________
c) What is the magnitude of the acceleration of the block?
Ans. ________________
d) What is the tension in the string that makes an angle of
37° with the rod?
Ans. ________________
e) What is the tension in the horizontal string?
Ans. ________________
(22 pts) 2. A small block with mass m = 0.20 kg is placed against a
spring that
is compressed 0.05 m. The spring is released, and the block travels a
distance of 1.8 m along a 37° incline before starting to slide back down.
Friction can be neglected.
a) How much potential energy was originally stored in the spring?
Ans. ______________
b) What is the kinetic energy of the block after it has traveled a distance of
0.80 m along the incline from its initial position?
Ans. ______________
(20 pts) 3. A 5.0 kg block slides along a horizontal tabletop, slides off
the edge, and falls to the floor. When the block is 2.0 m from the edge
(point A) its kinetic energy is 45 J. The coefficient of kinetic friction
between the block and the tabletop is µk = 0.40 and the
tabletop is a vertical distance of 0.80 m above the floor.
a) How much work is done by the friction force when the block travels 2.0 m
from point A to the edge of the tabletop (point B)?
Ans. ______________
b) What is the kinetic energy of the block when it reaches point B?
Ans. ______________
c) What is the kinetic energy of the block just before it strikes the
floor (point C)?
Ans. _____________
(18 pts) 4. A 20 kg block sliding to the right on a horizontal frictionless
surface collides with a 40 kg block that is initially at rest. After the
collision the 20 kg block is traveling perpendicular to its initial velocity
and the 40 kg block is traveling at 8 m/s in the direction
shown.
a) What is the speed vA2 of the 20 kg block after the
collision?
Ans. _______________
b) What is the speed vA1 of the 20 kg block before the
collision?
Ans. ______________
(20 pts) 5. A bullet with mass mA = 0.040 kg is fired
horizontally with speed vA1 at a block with mass
mB = 1.96 kg that is initially at
rest on a horizontal surface. The bullet strikes the block, remains
embedded inside it, and as a result of the collision the block slides a
distance of 3.5 m along the horizontal surface. The coefficient of
kinetic friction between the block and the surface is µk = 0.20.
a) What is the magnitude of the velocity of the block (with the bullet inside)
just after the collision is over?
Ans. ________________
b) What is the speed of the bullet just before the collision?
Ans. _______________