Uniform Circular Motion – Practice Multiple Choice
Test
1. 
A racecar is traveling in uniform
circular motion around a racetrack.
What happens to the centripetal acceleration of the car if the speed
is doubled but the radius of the circle remains constant? 
A) 
It remains the same. 
B) 
It increases by a factor of 2. 
C) 
It increases by a factor of 4. 
D) 
It is decreased by a factor of
onehalf. 
E) 
It is decreased by a factor of
onefourth. 
A small car of mass M travels along
a straight, horizontal track. As
suggested in the figure, the track then bends into a vertical circle of
radius R. 

2. 
What is the minimum acceleration that
the car must have at the top of the track if it is to remain in contact with
the track? 
A) 
4.91 m/s^{2}, downward 
B) 
4.91 m/s^{2}, upward 
C) 
9.81 m/s^{2}, upward 
D) 
9.81 m/s^{2}, downward 
E) 
19.6 m/s^{2}, upward 
3. 
A boy is whirling a stone around his
head by means of a string. The string
makes one complete revolution every second, and the tension in the string,F_{T}_{, }is directed horizontally. The boy then speeds up the stone, keeping
the radius of the circle constant, so that the string makes two complete
revolutions every second. What happens
to the tension in the sting? 
A) 
The tension is unchanged. 
B) 
The tension reduces to half of its
original value. 
C) 
The tension increases to twice its
original value. 
D) 
The tension increases to four times
its original value. 
E) 
The tension reduces to onefourth of
its original value. 
4. 
A certain string just breaks when it
is under 400 N of tension. A boy uses
this string to whirl a 10kg stone in a horizontal circle of radius 10
m. The boy continuously increases the
speed of the stone. At approximately
what speed will the string break? Assume the tension force is directed
horizontally. 
A) 
10 m/s 
B) 
20 m/s 
C) 
80 m/s 
D) 
100 m/s 
E) 
400 m/s 
5. 
Which force is responsible for holding
a car in an unbanked curve? 
A) 
the car's weight 
B) 
the force of friction 
C) 
the reaction force to the car's weight

D) 
the vertical component of the normal
force 
E) 
the horizontal component of the normal
force 
6. 
A satellite is placed in equatorial
orbit above Mars, which has a radius of 3397 km and a mass M_{M} = 6.40 10^{23}
kg. The mission of the satellite is to
observe the Martian climate from an altitude of 488 km. What is the orbital period of the
satellite? 
A) 
9.18 10^{2} s 
B) 
3.62 10^{3} s 
C) 
7.36 10^{3} s 
D) 
1.08 10^{5} s 
E) 
7.27 10^{12} s 
7. 
Determine the minimum angle at which a
roadbed should be banked so that a car traveling at 20.0 m/s can safely
negotiate the curve without the aid of friction. The radius of the curve is
2.00 x 10^{2} m. 
A) 
0.200° 
B) 
0.581° 
C) 
11.5° 
D) 
19.6° 
E) 
78.2° 
8. 
A 0.25kg ball attached to a string is
rotating in a horizontal circle of radius 0.5 m. Assume the tension force is
directed horizontally. If the ball revolves twice every second, what is the
tension in the string? 
A) 
2 N 
B) 
5 N 
C) 
7 N 
D) 
10 N 
E) 
20 N 
9. 
Consider a hypothetical planet in our
solar system whose average distance from the Sun is about four times that of
Earth. Determine the orbital period
for this hypothetical planet. 
A) 
0.25 year 
B) 
2.5 years 
C) 
4 years 
D) 
8 years 
E) 
16 years 
10. 
A plane is traveling at 200 m/s
following the arc of a vertical circle of radius R. At the top of its path, the passengers
experience "weightlessness."
To one significant figure, what is the value of R? 
A) 
200 m 
B) 
1000 m 
C) 
2000 m 
D) 
4000 m 
E) 
40 000 m 
Answer Key
1. 
C 
2. 
D 
3. 
D 
4. 
B 
5. 
B 
6. 
C 
7. 
C 
8. 
E 
9. 
D 
10. 
D 