Test A
1)
TEST 2: PHYSICS 103
ASSUME g=10 m/s2 FOR ALL PROBLEMS
Ahriel drives her 1000 kg car travels around a flat circular path of radius 20 m at
constant speed. If the maximum frictional force between the road and the tires is
80,000 N, which of the following statements is true:
A.
B.
C.
D.
E.
The net force on the car is zero
The net force on the car must be more than 80,000 N
The maximum velocity she can go without skidding is 40 m/s
The maximum velocity she can go without skidding is 20 m/s
None of these
2) A piece of chalk has a mass of 0.1 kg and is revolving in a vertical circle at constant
speed at the end of a string. If the length of the string is 0.5 m and the chalk makes one
revolution in 1 second, approximately what is the tension in the string when the chalk
is at its highest point in the circle?
A. 0.97 N
B. 1.97 N
C. 2.97 N
D. 1 N
E. None of these
3)
As the moon circles the earth, the net force on it is:
A. zero
B. directed towards the earth
C. directed away from the earth
D. in the same direction as its velocity
E. It depends on where it is
4)
Elise and Keith run on a track at a constant speed of 10 mph. If Elise travels along
the inner radius of the track and Keith travels along the outer radius and they both have the
same mass, which of the following statements must be true:
A. The centripetal force on both students is the same
B. The centripetal force on Elise is greater than on Keith
C. The force of friction between the track and Keith is greater than that for
Elise
D. Both students complete the race in the same time.
E. None of these
5)
What other force balances the downward pull of gravity on a NASA satellite while
it is in orbit around Earth?
A. The centrifugal force
B. The force created by its velocity
C. The acceleration
D. A balancing force is not needed since there is no net force on the satellite
E. There is no balancing force- gravity is the only force acting on the satellite.
Test A
6) Hasan’s normal weight is 600 newtons. How much will he weigh while orbiting in a
satellite 12,000 km (two earth radii) above the surface of the Earth?
A. Zero, since he would be weightless
B. 67 N
C. 150 N
D. 300 N
E. 600 N
7) You decide to go on a Ferris wheel of radius 30m after your PHYS 103 class and this
time you decide to stand on a scale during the ride. The scale reads 600 N when you are
standing still on the ground before you start the ride. If the scale reads 800 N at the bottom
of the cycle when you’re moving during the ride, then the Ferris wheel must be going at a
velocity of:
A. 20 m/s
B. 10 m/s
C. 17.32 m/s
D. More information is needed
E. 26.46 m/s
8)
The fastest moving planet in our solar system is
A. The smallest planet
B. The most massive planet
C. the planet nearest the Sun
D. the planet farthest from the Sun
E. any planet, for they all move at the same speed around the Sun
9)
One of the Apollo missions went into orbit around the moon. It took 1.2 hours to
go around the moon at a radius of orbit of 1700 km. What is the mass of the moon?
A. 5  106 kg
B. 0.2 kg
C. 1.5  1023 kg
D. 5  1028 kg
Test A
10) An elephant and a mouse are both in orbit around the earth and are both at the same
distance from the surface of the earth. Which of the following statements is true?
A. The mouse is going faster around the earth
B. The elephant is going faster around the earth
C. Both objects are traveling at the same speed around the Earth
D. The force of gravity between the Earth and each object is the same
E. Both C and D
11) You push your physics book across the table. The book weighs 8 N, you push with a
steady 5 N horizontal force, and the force of friction against the book is 3 N. If you
push the book a distance of 3 m, the amount of work you do on the book is:
A.
B.
C.
D.
15 J
24 J
9J
4J
12)
I drop a 1 kg book from a height of 1 m, what is the velocity of the book as it hits
the floor 1 m below if it loses 2 J of energy through air resistance:
A. 4 m/s
B. 4.47 m/s
C. 19.6 J
D. 6 m/s
E. Not enough information
13)
A 1 kg ball dropped from a height of 2 m rebounds only 1.5 m after hitting the
ground. The amount of energy converted into heat is about
A. 0.5 J
B. 1.0 J
C. 1.5 J
D. 5 J
14)
Consider the frictionless roller coaster shown below. What is the maximum height
the roller coaster will achieve as it ascends the second hill?
A. 100 m
B. slightly more than 100 m
C. slightly less than 100 m
D. Much less than 100 m
Test A
5 m/s
100 m
15)
In class I did a demo releasing a ball on an incline that rolls into a loop (“loop-theloop”) as pictured below. Ignoring friction and the rotational motion of the ball, if the
radius of the loop is R, the maximum height at which I would need to release the ball in
order for it to stay on the track as it goes around the loop is:
A.
B.
C.
D.
E.
2R
R
5/2R
3/2R
3R
16)
Elise runs East, head on into a 400 lb sumo wrestler running towards her (West) at
one quarter her speed (sorry, Elise). If Elise weighs 100 lb and the two have an
inelastic collision, after the collision, they will:
A. both move West
B. both move East
C. both be at rest
D. cannot be determined.
17)
A 5000 kg freight car runs into a 10,000 kg freight car at rest. They couple upon
collison and move with a speed of 2 m/s. What was the initial speed of the 5000 kg
car?
A. 4 m/s
B. 5 m/s
C. 6 m/s
D. 8 m/s
Test A
18)
A 1 kg glider and a 2 kg glider both slide toward each other at 1 m/s on an air track.
They collide and stick. The combined mass moves at
A. 0 m/s
B. 1/2 m/s
C. 1/3 m/s
D. 1/6 m/s
19)
Consider the frictionless roller coaster below. The velocity at the top of the second
hill is approximately
A. 15 m/s
B. zero
C. 25 m/s
D. 5 m/s
15 m/s
50 m
60 m
20) Brad lifts his 2 kg book without acceleration a height of 2m. Neglecting air resistance,
the amount of work he does is:
A.
B.
C.
D.
E.
Zero, since then net force is zero
40 J
4J
2J
Not enough information
Test A
Extra-credit Challenge Problems:
21) A 0.2 kg ball is twirled at constant speed at the end of a string in a vertical circle of
radius 0.5 m at the top of a hill as shown below. The tension in the string when the ball is
at its highest point is 8N. If the string breaks while you are twirling it at this point and the
height of the ball above the bottom of the hill is 20 m, what will the approximate speed of
the ball as it hits the ground? (This was a problem from a student last year)
A. 20.6 m/s
B. 24.5 m/s
C. 14 m/s
D. 60 m/s
E. Not enough information provided
0.2 kg
20 m
22) A 10g bullet is fired into a 200g block of wood at rest on a horizontal surface. After
impact, the block slides 8 m before coming to rest. If the coefficient of friction, =0.4,
find the speed of the bullet before impact. Note that the frictional force acting on an object
is F=N, where N is the normal force.
A. 106 m/s
B. 168 m/s
C. 226 m/s
D. 286 m/s
E. Not enough information provided
Test A
Units and constants
1 m = 100 cm
1 km = 1000 m
G = 6.67 10-11 N m2/kg2
Mass of Earth = 5.98 1024 kg
Radius of Earth = 6380 km
1 inch = 2.54 cm
1 m = 3.28 ft
1 mile = 5280 ft
1 mile = 1.61 km
1 kg=1000 g
Formulae:
For constant velocity: (here t is time and d is distance)
v
d
t
For constant acceleration: (here v is the change in velocity and t is time)
a
v
t
For anything moving at constant acceleration, the position can be found using:
d = d0 + vo . t + ½ a.t2 where d is the final position after time t, d0 is the initial position, t
is the time, a is the acceleration, and vo is the initial velocity
For anything moving at constant acceleration, the final velocity (v ) can be found using:
v= vo + a. t
From Newton’s second law:
F=m.a
Where F is the net force on the object, m is the mass and a is its acceleration. The units are
Newtons if mass is in kg and a is in m/s2
Test A
A few math formulae and unit conversion factors:
Quadratic equation and solution
ax2  bx  c  0
x
- b  b 2 - 4ac
2a
Centripetal Force:
F=mv2/r
(Note the circumference of a circle = 2r)
Gravitation:
F=Gm1m2/r2
G = 6.67 10-11 N m2/kg2
Work and Energy:
Work = Force . distance
(where force is along direction of distance traveled)
Gravitational Potential Energy
PE = m.g.h
(where m is mass, and h is height)
Kinetic Energy
KE = 1/2m.v2
(where m is mass, and v is velocity)
Momentum
P= m.v
( where m is mass and v is velocity)
Momentum before = momentum after (momentum is conserved when there are no external
forces; we assume this is true during collisions)