Download Practice Test 1. An object moving along the x axis is acted upon by a

Practice Test
1.
An object moving along the x axis is acted upon by a force Fx that varies with
position as shown. How much work is done by this force as the object moves
from x = 2 m to x = 8 m?
Fx (N)
20
10
0
2
4
6
8
10 12
x (m)
–10
a.
b.
c.
d.
e.
–10 J
+10 J
+30 J
–30 J
+40 J
c
2.
As a 2.0-kg object moves from (2 ˆi + 5 ˆj) m to (6 ˆi − 2 ˆj) m, the constant resultant
force acting on it is equal to 4 ˆi − 3ˆj) N. If the speed of the object at the initial
position is 4.0 m/s, what is its kinetic energy at its final position?
a.
b.
c.
d.
e.
62 J
53 J
73 J
86 J
24 J
b
3.
A 10-kg block on a horizontal frictionless surface is attached to a light spring
(force constant = 0.80 kN/m). The block is initially at rest at its equilibrium
position when a force (magnitude P = 80 N) acting parallel to the surface is
applied to the block, as shown. What is the speed of the block when it is 13 cm
from its equilibrium position?
P
a.
b.
c.
d.
e.
0.85 m/s
0.89 m/s
0.77 m/s
0.64 m/s
0.52 m/s
a
4.
Positive work can be done
a.
b.
c.
d.
e.
by friction when a car is accelerating without skidding.
by a spring when it launches a clown in the air.
by a hand throwing a ball.
by all of the above.
only by (b) and (c) above.
e
5.
A certain pendulum consists of a 1.5-kg mass swinging at the end of a string
(length = 2.0 m). At the lowest point in the swing the tension in the string is
equal to 20 N. To what maximum height above this lowest point will the mass
rise during its oscillation?
a.
b.
c.
d.
e.
77 cm
50 cm
63 cm
36 cm
95 cm
d
6.
A skier weighing 0.80 kN comes down a frictionless ski run that is circular
(R = 30 m) at the bottom, as shown. If her speed is 12 m/s at point A, what is her
speed at the bottom of the hill (point B)?
40˚
40
30 m
A
B
a.
b.
c.
d.
e.
17 m/s
19 m/s
18 m/s
20 m/s
12 m/s
a
7.
The only force acting on a 2.0-kg object moving along the x axis is shown. If the
velocity vx is –2.0 m/s at t = 0, what is the velocity at t = 4.0 s?
Fx (N)
4
0
1
2
3
–4
–8
a.
b.
c.
d.
e.
–2.0 m/s
–4.0 m/s
–3.0 m/s
+1.0 m/s
+5.0 m/s
4
t (s)
c
8.
A 4.0-kg particle is moving horizontally with a speed of 5.0 m/s when it strikes a
vertical wall. The particle rebounds with a speed of 3.0 m/s. What is the
magnitude of the impulse delivered to the particle?
a.
b.
c.
d.
e.
24 N ⋅ s
32 N ⋅ s
40 N ⋅ s
30 N ⋅ s
8.0 N ⋅ s
b
9.
A 3.00 kg stone is dropped from a 39.2 m high building. When the stone has
fallen 19.6 m, the magnitude of the impulse it has received from the gravitational
force is
a.
b.
c.
d.
e.
9.8 N ⋅ s.
19.6 N ⋅ s .
29.4 N ⋅ s.
58.8 N ⋅ s.
117.6 N ⋅ s.
d
10.
If M = 0.50 kg, L = 1.2 m, and the mass of each connecting rod shown is
negligible, what is the moment of inertia about an axis perpendicular to the
paper through the center of mass? Treat the mass as particles.
M
a.
b.
c.
d.
e.
d
L
3.7 kg ⋅ m2
2.8 kg ⋅ m2
3.2 kg ⋅ m2
2.3 kg ⋅ m2
3.9 kg ⋅ m2
M
L
3M
11.
A uniform sphere of radius R and mass M rotates freely about a horizontal axis
that is tangent to an equatorial plane of the sphere, as shown below. The moment
of inertia of the sphere about this axis is
a.
b.
c.
d.
e.
2
MR
5
2
MR
3
5
MR
7
7
MR
5
3
MR
2
2
.
2
.
2
.
2
.
2
.
d
12.
A particle located at the position vector r = (i + j) m has a force F = (2i + 3j) N
acting on it. The torque about the origin is
a.
(1 k )N · m
b.
(5 k )N · m
c.
(–1 k )N · m
d.
(–5 k )N · m
e.
(2 i + 3 j )N · m
a
13.
A massless rope is wrapped around a uniform cylinder that has radius R and
mass M, as shown in the figure. Initially, the unwrapped portion of the rope is
vertical and the cylinder is horizontal. The linear acceleration of the cylinder is
a.
b.
c.
d.
e.
(2/3)g
(1/2)g
(1/3)g
(1/6)g
(5/6)g
a
14.
A pendulum bob of mass m is set into motion in a circular path in a horizontal
plane as shown in the figure. The square of the angular momentum of the bob
about the vertical axis through the point P is
P
θ
a
a.
m2 g 3 sin4 θ/cos θ
b.
m2 g 3 sin3 θ/cos θ
c.
m2 g
3
sin2 θ/cos θ
d.
m2 g
3
sin θ/cos θ
e.
2
3
sin2 θ
m g
15.
The diagrams below show forces applied to a wheel that weighs 20 N. The
symbol W stands for the weight. In which diagram(s) is the wheel in
equilibrium?
20 N
20 N
10 N
10 N
10 N
10 N
10 N
10 N
10 N
10 N
a.
b.
c.
d.
e.
W
W
W
W
(a)
(b)
(c)
(d)
A
B
C
D
A and C
c
16.
L
is removed from one corner of a square sandwich that has
2
sides of length L. The center of mass of the remainder of the sandwich moves
from C to C’. The displacement of the x coordinate of the center of mass (from C
to C’) is
A square of side
y
L
C′
C
x
a.
b.
c.
d.
e.
1
L.
12
2
L.
12
1
L.
6
1
L.
8
2
L.
8
a
17.
One of the curators at the art museum is tilting a large cylinder backward. At
what angle θ will the cylinder of height h and radius r be in unstable
equilibrium?
2r
h
θ
a.
θ = sin−1⎛⎜
2r⎞
⎟.
⎝ h⎠
⎛ 2r⎞
= cos−1⎜ ⎟ .
⎝ h⎠
⎛ 2r⎞
= tan−1⎜ ⎟ .
⎝ h⎠
⎛ r⎞
= sin−1⎜ ⎟ .
⎝ h⎠
⎛ r⎞
= tan−1⎜ ⎟ .
⎝ h⎠
b.
θ
c.
θ
d.
θ
e.
θ
c
18.
Pairs of forces of equal magnitude act on identical cylinders as shown in the
figures. In which example is the cylinder in translational and rotational
equilibrium?
(a)
(d)
b
(c)
(b)
(e )
19.
Sebastian has drawn a free-body diagram for a ladder of mass m leaning against
a frictionless wall. His diagram is shown below.
N
P
FEarth on ladder
fs
a.
b.
c.
d.
e.
f s is in the wrong direction.
P should be directed upwards, not down.
P should be perpendicular to the wall, not parallel to it.
N should be down into the floor for f s to have the given direction.
P is correct, but there should also be a force perpendicular to the wall.
c
20.
The figure below shows a planet traveling in a counterclockwise direction on an
elliptical path around a star located at one focus of the ellipse. When the planet is
at point A,
STAR
A
a.
b.
c.
d.
e.
its speed is constant.
its speed is increasing.
its speed is decreasing.
its speed is a maximum.
its speed is a minimum.
c
21.
Two identical planets orbit a star in concentric circular orbits in the star’s
equatorial plane. Of the two, the planet that is farther from the star must have
a.
b.
c.
d.
e.
the smaller period.
the greater period.
the smaller gravitational mass.
the larger gravitational mass.
the larger universal gravitational constant.
b
22.
A 50-kg satellite circles the Earth in an orbit with a period of 120 min. What
minimum energy is required to change the orbit to another circular orbit with a
period of 180 min? (Earth: radius = 6.4 × 106 m, mass = 6.0 × 1024 kg)
a.
b.
c.
d.
e.
2.9 × 108 J
3.5 × 108 J
4.1 × 108 J
4.7 × 108 J
5.9 × 108 J
a
23.
As an object moves from point A to point B only two forces act on it: one force is
conservative and does –70 J of work, the other force is nonconservative and does
+50 J of work. Between A and B,
a.
b.
c.
d.
e.
the kinetic energy of object increases, mechanical energy increases.
the kinetic energy of object decreases, mechanical energy increases.
the kinetic energy of object decreases, mechanical energy decreases.
the kinetic energy of object increases, mechanical energy decreases.
None of the above.
b
24.
An astronaut tosses a ball out in space where gravitational forces may be
neglected. What will happen to the ball?
a.
b.
c.
d.
e.
It will stop as soon as the force the astronaut gave it is used up.
It will stop when the energy the astronaut gave it runs out.
It will stop after a short time because there is no gravity to keep it moving.
It will move in a circle like a boomerang.
It will be slowed down very gradually by collisions with molecules in space.
e
25.
A uniform ladder 15 ft long is leaning against a frictionless wall at an angle of 53°
above the horizontal. The weight of the ladder is 30 pounds. A 75-lb boy climbs
6.0-ft up the ladder. What is the magnitude of the friction force exerted on the
ladder by the floor?
a.
b.
c.
d.
e.
b
43 lb
34 lb
38 lb
47 lb
24 lb