Physics 201 MWF10:20 Fall 1997 (Ford)
Final Exam Chapts. 1--23 in SZY College Physics
Show all your work. Partial credit will be given if earned. Write your
answers in the blanks provided.
(9 pts) 1. A Carnot refrigerator takes heat from water at 0 °C and gives
off heat to a room at 27 °C. Suppose that 0.200 kg of water
at 0 °C is converted to ice at 0 °C by the refrigerator.
a) QC, the heat absorbed by the refrigerator from the water at 0 °C;
Ans. ____________________
b) QH, the heat rejected to the room at 27 °C;
Ans. _________________
c) W, the mechanical energy that must be supplied to the refrigerator.
Ans. _________________
(12 pts) 2. A football kicked from ground level at a speed of
40 m/s and at an angle of 53° above the horizontal
strikes the wall of a tall building 4.0 s after being kicked.
a) What is the horizontal distance from the point where the football was kicked
to the base of the building?
Ans. __________________
b) What is the maximum height above ground reached by the ball during its
motion?
Ans. __________________
c) What is the magnitude of the velocity of the ball just before it strikes
the building?
Ans. ___________________
(11 pts) 3. A uniform bar 8 m long and weighing 120 N is attached at
one end to a
wall by a frictionless hinge. The bar is held at an angle of 37° above
the horizontal by a horizontal cable.
a) What is the tension in the cable?
Ans. __________________
b) What are the horizontal and vertical components of the force the hinge
exerts on the bar?
Ans. horizontal ________________
vertical ___________________
(6 pts) 4. A source of sound waves approaches a stationary listener at a speed
of 20 m/s. The speed of sound in the air is 345 m/s.
If the listener hears a frequency of 240 Hz, what is the frequency emitted
by the source?
Ans. _________________
(10 pts ) 5. A small block on a frictionless surface has a mass of 0.050 kg and
is attached to a string that passes through a hole in the surface.
a) The block is originally revolving at a distance of 0.30 m from the hole
with an angular velocity of 4.0 rad/s. What is the tension in the
string?
Ans. ___________________
b) The string is now slowly pulled from below, shortening the radius of the
circle in
which the block revolves to 0.10 m. What now is the tension in the string?
Ans. ________________
(12 pts) 6. The system sketched below is released from rest, and the hanging
block of mass m is observed to move downward a distance of 6.0 m in a
time of 2.0 s. The coefficient of friction between the horizontal surface
and the 8.0 kg block is µk = 0.2. The pulley is massless and
fricitionless. Calculate:
a) the acceleration of the hanging block.
Ans. ________________
b) the friction force acting on the 8.0 kg block while it is moving.
Ans. ___________________
c) the tension in the rope connecting the blocks while the blocks are
moving.
Ans. ____________________
d) the mass m of the hanging block.
Ans.___________________
(10 pts) 7. It is found that a force P = 20 N applied to a box keeps
the box
sliding along the floor at constant speed. The box weighs 50 N, and as the
sketch shows, the direction of P is at 37° below the horizontal.
a) What is the magnitude of the normal force exerted on the moving box
by the floor?
Ans. ___________________
b) What is the coefficient of kinetic friction µk between the
box and the floor?
Ans. ____________________
(6 pts) 8. A cork moves up and down in a periodic way because of waves on the
surface of a lake. It takes 0.5 s for the cork to travel from the highest point
to its lowest. The distance between crests (peaks) of the waves on the
surface of the water is 2.0 m.
a) What is the wavelength of these waves?
Ans. _______________________
b) What is the frequency of these waves?
Ans. ________________________
c) How fast are these waves traveling?
Ans. _______________________
(12 pts) 9. A block with mass 2 kg is placed on a spring that is compressed
0.5 m, so that 80 J of potential energy is stored in the spring. The
spring is released, and the block travels vertically upward.
a) What is the maximum height reached by the block, measured from the initial
position from which it is released?
Ans. ___________________
b) What is the speed of the block when it is 1.5 m above its initial position?
Ans. __________________
(12 pts) 10. A bullet with mass mA = 0.020 kg
is fired horizontally with a speed
of 200 m/s at a block with mass mB = 1.98 kg that is initially
at rest on a frictionless horizontal surface. The block is attached to a spring
of force constant k = 80.0 N/m. The other end of the spring is
attached to the wall. The bullet strikes the block, remains embedded inside
it, and as a result of the collision the block moves to the right, compressing
the spring.
a) What is the speed of the block just after the collision, when the block and
bullet have come to the same speed?
Ans. ___________________
b) What is the maximum distance the spring is compressed?
Ans. ______________