1. A ball moves with a constant speed of 4 m/s around a circle of radius 0.25 m. What is the period of the motion?
A.0.1 s
B.0.4 s
C.0.7 s
D.1 s
E.2 s


2. A racecar is traveling at constant speed around a circular track. What happens to the centripetal acceleration of the car if the speed is doubled?
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 one-half.
E.It is decreased by a factor of one-fourth.


3. A 0.25-kg ball attached to a string is rotating in a horizontal circle of radius 0.5 m. If the ball revolves twice every second, what is the tension in the sting?
A.2 N
B.5 N
C.7 N
D.10 N
E.20 N


4. In an amusement park ride, a small child stands against the wall of a cylindrical room that is then made to rotate. The floor drops downward and the child remains pinned against the wall. If the radius of the device is 2.15 m and the relevant coefficient of friction between the child and the wall is 0.400, with what minimum speed is the child moving if he is to remain pinned against the wall?
A.7.26 m/s
B.3.93 m/s
C.12.1 m/s
D.5.18 m/s
E.9.80 m/s


5. Which force is responsible for holding a car in a frictionless banked curve?
A.the reaction force to the car's weight
B.the vertical component of the car's weight
C.the vertical component of the normal force
D.the horizontal component of the car's weight
E.the horizontal component of the normal force


6. 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


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 if the radius of the curve is 2.00 ´ 102 m.
A.0.200°
B.0.581°
C.11.5°
D.19.6°
E.78.2°


8. A car enters a horizontal, curved roadbed of radius 50 m. The coefficient of static friction between the tires and the roadbed is 0.20. What is the maximum speed with which the car can safely negotiate the unbanked curve?
A.5 m/s
B.10 m/s
C.20 m/s
D.40 m/s
E.100 m/s


9. The earth exerts the necessary centripetal force on an orbiting satellite to keep it moving in a circle at constant speed. Which statement best explains why the speed of the satellite does not change even though there is a net force exerted on it?
A.The satellite is in equilibrium.
B.The acceleration of the satellite is 0 m/s2.
C.The centripetal force has magnitude mv2/r.
D.The centripetal force is canceled by the reaction force.
E.The centripetal force is always perpendicular to the velocity.


10. Consider a satellite in a circular orbit around the Earth. If it were at an altitude equal to twice the radius of the Earth, 2RE, how would its speed v be related to the Earth's radius RE, and the magnitude g of the acceleration due to gravity on the Earth's surface?
A.

B.

C.

D.

E.



11. An object weighs 10 N on the earth's surface. What is the weight of the object on a planet that has one tenth the earth's mass and one half the earth's radius?
A.4 N
B.2 N
C.1 N
D.10 N
E.20 N


12.
A 2400-kg satellite is in a circular orbit around a planet. The satellite travels with a constant speed of 6.67 ´ 103 m/s.
The radius of the circular orbit is 8.92 ´ 106 m.
R-1 Ref 5-3

At the instant shown in the figure, which arrow indicates the direction of the net force on the satellite?


Answer:



13. A spaceship is in orbit around the earth at an altitude of 12 000 miles. Which one of the following statements best explains why the astronauts experience "weightlessness?"
A.The centripetal force of the earth on the astronaut in orbit is zero newtons.
B.The pull of the earth on the spaceship is canceled by the pull of the other planets.
C.The spaceship is in free fall and its floor cannot press upwards on the astronauts.
D.The force of gravity decreases as the inverse square of the distance from the earth's center.
E.The force of the earth on the spaceship and the force of the spaceship on the earth cancel because they are equal in magnitude but opposite in direction.


14. A 25-kg box is sliding down an ice-covered hill. When it reaches point A, the box is moving at 11 m/s. Point A is at the bottom of a circular arc that has a radius R = 7.5 m. What is the magnitude of the normal force on the box at Point A?

A.250 N
B.280 N
C.400 N
D.650 N
E.900 N


15.
A 1500-kg car travels at a constant speed of 22 m/s around a circular track that has a radius of 85 m.
R-2 Ref 5-5

What is the average velocity of the car during one revolution?
A.8.0 m/s
B.12 m/s
C.26 m/s
D.44 m/s
E.zero m/s




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