PHYSICS 101 - FINAL EXAM - SPRING 2015
NAME:
Please circle your section number:
§01- 10:00
§02- 11:00
§03- 17:00
§04- 14:00
Rahul Parelkar
Rahul Parelkar
Olga Kyzylova
Daryl Omire-Mayor
§05- 09:00
§06- 14:00
§09- 15:00
§10- 10:00
Michael Meyers
Olga Kyzylova
Daryl Omire-Mayor
§11- 11:00
§12- 17:00
§13- 15:00
Michael Meyers
Daryl Omire-Mayor
Olga Kyzylova
Michael Meyers
For full credit: show all work, units and the correct number of significant figures.
8 problems (13 pts each).
g = 9.8 m/s
2
G = 6.67 × 10−11 N · m2 /kg2
USEFUL INFORMATION:
1 horsepower(HP ) = 746 W
MEarth = 5.97 × 1024 kg
REarth = 6.37 × 106 m
Problem 1. (13 points)
If a bullet that leaves the muzzle of a gun at 250 m/s is to hit a target 100 m away at the level of
the muzzle, the gun must be aimed at a point above the target. How far above the target is that
point? (Ignore any effects due to air).
Problem 2. (13 points)
The speed of the head of a redheaded woodpecker reaches 5.5 m/s before impact with the tree. If
the mass of the head is 0.060 kg and the average force on the head during impact is 12.0 N, find
(a) the acceleration of the head (assuming constant acceleration), (b) the depth of penetration into
the tree, and (c) the time it takes for the head to come to a stop.
Problem 3. (13 points)
A block of mass m1 = 250 g is at rest on a plane that makes an angle of θ = 30◦ with the horizontal.
The coefficient of kinetic friction between the block and the plane is 0.100. The block is attached
to a second block of mass m2 = 200 g that hangs freely by an ideal string that passes over a
frictionless, massless pulley (See the figure). When the second block has fallen 30.0 cm, what will
be its speed?
Problem 4. (13 points)
A 3.50-kN piano is lifted by three workers at constant speed to an apartment 25.0 m above the
street using a pulley system fastened to the roof of the building. Each worker is able to deliver 165
W of power, and the pulley system is 75.0% efficient (so that 25.0% of the mechanical energy is lost
due to friction in the pulley). Neglecting the mass of the pulley and ropes, find the time required
to lift the piano from the street to the apartment.
Problem 5. (13 points)
The magnitude of the single force acting on a particle of mass m is given by F = bx2 where b is
a constant. The particle starts from rest. After it travels a distance L, determine its (a) kinetic
energy and (b) speed.
Problem 6. (13 points)
A block of mass m on a horizontal frictionless tabletop is pushed against a horizontal spring,
compressing it a distance x, and the block is then released. The spring propels the block along the
tabletop, giving a speed v. The same spring is then used to propel a second block of mass 4m,
giving it a speed 3v. What distance was the spring compressed in the second case? Express your
answer in terms of x.
Problem 7. (13 points)
A 0.030-kg bullet is fired vertically at 200 m/s into a 0.15-kg baseball that is initially at rest. How
high does the combined bullet and baseball rise after the collision, assuming the bullet embeds itself
in the ball?
Problem 8. (13 points)
A massless horizontal disc of radius 2 m is rotating in a horizontal plane about a frictionless axle.
A man (mass = 60 kg ) standing on the rim of the disc walks slowly from the rim toward the center.
The angular velocity of the disc is 2 rad/s as the man begins to walk.
(a) Calculate the man’s angular momentum. (4 points)
(b) What is his angular velocity as he reaches a point 0.5 m from the axis? (5 points)
(c) How much work is done by the man in walking the 1.5-m distance? (4 points)