Physics Review - Circular Motion

a, 6.42 x 10^23 kg

Phobos, a moon of Mars, has an orbital period of 7.65 hours. If the radius of Phobos' orbit is 9.37 x 10^6 m, then the mass of Mars is closest to: a. 6.42 x 10^23 kg b. 5.97 x 10^24 c. 9.76 x 10^26 d. 1.87 x 10^27 e. 5.27 x 10^28

a, 72 kg

The acceleration of gravity on the moon is 1/6 what it is on earth. An object of mass 72 kg is taken to the moon, what is its mass there? a. 72 kg b. 12 kg c. 72 N d. 12 N

c, to take the turn at a faster speed

The banking angle in a turn of the olympic bobsled track is not constant, but increases upward from the horizontal. Coming around a turn, the bobsled team will intentionally "climb the wall" then go lower coming out of the turn. Why do they do this? a. to prevent the bobsled from turning over b. to reduce the g force on them c. to take the turn at a faster speed d. bc it looks cool

b, 40N

The centripetal force on the ball in the problem above is a. 10N b. 40N c. 20N d. 80N

d, the gravitational pull of the earth

The force needed to keep the moon in orbit is provided by a. inertia b. its rotation on its axis c. the gravitational pull of the sun d. the gravitational pull of the earth

c, Kepler

"The square of a planet's orbital period is directly proportional to the cube of its orbital radius." This statement is attributable to which of the following scientists? a. Galileo b. Copernicus c. Kepler d. Newton e. Einstein

b, yes, this is possible if the speed is changing

Is it possible for an object moving around a circular path to have both centripetal and tangential acceleration? a. no, bc the path would not be a circle b. yes, this is possible if the speed is changing c. no, an object can only have one or the other at any given time d. yes, this is possible if the speed is constant

c, yes, an object can accelerate by changing direction at a constant speed.

Is it possible for an object moving with a constant speed to accelerate? a. no, an object accelerates only when it speeds up. b. no, if the speed is constant then the acceleration is equal to zero. c. yes, an object can accelerate by changing direction at a constant speed. d. yes, because constant speed requires a net nonzero acceleration.

d, the stopper is already in motion

Johnny Physics twirls a rubber stopper on the end of a string in a horizontal circle above his head. If he is pulling on the string, why doesn't the stopper move towards his hand? a. gravity pulls on the stopper b. the tension in the sting is greater than the stopper's weight c. a force is pushing the stopper to the outside of the circle d. the stopper is already in motion

d, 80 m/s2

A .5 kg ball moves in circle with a radius of .4m at a speed of 5.657 m/s its centripetal acceleration is a. 10 m/s2 b. 40 m/s2 c. 20m/s2 d. 80 m/s2

d, 91.6 N

A 2 kg stone tied to the end of a string 1 m long is whirled in a vertical plane. When the stone passes through its lowest point, its speed is 6 m/s. What is the tension in the string? a. 19.6 N b. 52.5 N c. 72 N d. 91.6 N e. 98.8 N

e, 20 N

A 2.5 kg ball attached to a string is rotating in a horizontal circle of radius .5 m. Assume the tension force is directed horizontally. If the ball revolves twice every second, which of the following is closest to the tension in the string? a. 2N b. 5N c. 7N d. 10N e. 20N

d, 100 m

A 2000 kg care moves in a circle at a constant speed of 5 m/s. If 500 N is required to keep the car moving in a circle, what is the radius of the car's path? a. .01 m b. .16 m c. 6.25 m d. 100 m

d, 3.14 m/s

A bicyclist circles a track with at radius of 5 meters in 10 seconds. What is his speed? a. .5 m/s b. 3.14 m/s c. 2 m/s d. 3.14 m/s

d, twice as big

A car goes around a curve of radius R at a constant speed V, then goes around a curve of radius 2R at speed 2V. What is the centripetal force of the car as it goes around the second curve compared to the first? a. 1/2 as big b. 1/4 as big c. 4x as big d. twice as big

c, toward the curve's center

A car goes around a curve of radius R at a constant speed V. What is the direction of the net force on the car? a. toward the back of the car b. toward the front of the car c. towards the curve's center d. away from the curve's center

e, the car's acceleration directed toward the center

A car moves around a circular path of a constant radius at a constant speed. Which of the following statements is true? a. the car's velocity is constant in magnitude and direction b. the car's acceleration is constant in magnitude and direction c. the car's acceleration is 0 d. The car's velocity is directed toward the center e. the car's acceleration directed toward the center

b, 2o m/s

A certain string just breaks when it is under 400 N of tension, a student uses this string to whirl a 10 kg stone in a horizontal circle of radius 10 m. The student continuously increases the speed of the stone. At what Assume the tension force is directed horizontally. a. 20 m/s b. 20 m/s c. 80 m/s d. 100 m/s e. 400 m/s

c, 6.28 m/s

A ferris wheel with a radius of 20 m rotates at a constant rate of 3 revolutions every 60 seconds. What is the tangential velocity at the edge of the wheel, where the seats are? a. .o5 m/s b. 3.14 m/s c. 6.28 m/s d. 20 m/s

e, 5g

A pilot performs a vertical maneuver around a circle with a radius R. When the airplane is at the lowest point of the circle, the apparent weight of the pilot is 6mg. What is the acceleration at the lowest point? a. g b. 2g c. 3g d. 4g e. 5g

b, it decreases when he moves from the lowest to highest point of the circle

A pilot performs a vertical maneuver around a circle with a radius R. Which of the following is true about the pilot's apparent weight? a. it increases when he moves from the lowest to the highest point of the circle. b. it increases when he moves from the lowest to the highest point of the circle. c. it decreases when he moves from the highest to the lowest point of the circle. d. remains constant at all points e. more information is required.

e, 4000

A plane is travelling at 200 m/s following the arch of a vertical circle of radius R. At the top of its bath, the passengers experience "weightlessness" which of the following is the closest to the radius R to achieve this condition? a. .025 b. 20 c. 200 d. 400 e. 4000

a, g downward

A roller coaster car is on a track the forms a circular loop in the vertical plane. If the car is to just maintain contact with the track at the top of the loop, what is the minimum value for the centripetal acceleration at this point? a. g downward b. g upward c. .5 g downward d. 2g upward

d, it is never beyond the pull of earth's gravity

A spaceship is traveling to the moon, at what point is it beyond the pull of earth's gravity a. when it is closer to the moon than it is to earth b. when it is halfway there c. when it gets beyond the atmosphere d. it is never beyond the pull of earth's gravity

a, 7.7 x 10^3 m/s

Approximately how fast is the ISS moving through space in its orbit around the Earth? a. 7.7 x 10^3 m/s b. 8.3 x 10^5 m/s c. 6.0 x 10^7 m/s d. 3.0 x 10^8 m/s e. 3.6 x 10^15 m/s

d, 90 min

Approximately how many minutes does it take the ISS to complete one orbit around the Earth? a. 30 min b. 45 min c. 60 min d. 90 min e. 3600 min

c, decreases

As a rocket moves away from the earth's center, the rockets weight a. remains the same b. depends on how fast its moving c. decreases d. increases

a, the same

Compared to your mass on Earth, your mass on the Moon is a. the same b. less c. more d. half as much

c, 4y

Consider a hypothetical planet in our solar system whose average distance from the sun is about 2.5x that of earth. Which of the following is closes to the orbital period for this hypothetical planet? a. .25y b. 2.5 y c. 4y d. 8y e. 16y

b, it is moving in a circle

Consider a particle moving with constant speed such that its acceleration of constant magnitude is always perpendicular to its velocity a. it is moving in a parabola b. it is moving in a circle. c. it is moving in a straight line. d. non of the above is definitely true all of the time.

c, Statement I is true. Statement II is false.

Consider the following two statements: I. Astronauts experience "weightlessness" in a satellite in orbit around the Earth. II. The Gravitational force exerted by the Earth on astronauts is zero. Which of the following accurately describes the two statements above? a. Both statements are true and one statement can be used to explain the other. b. Both statements are true, but neither can be sued to explain the other. c. Statement I is true. Statement II is false. d. Statement I is false. Statement II is true. e. Both statements are false.

d, the square of the distance between the two masses

The gravitational force between two masses is inversely proportional to a. the distance between the two masses b. the square of the product of the two masses c. the product of the two masses d. the square of the distance between the two masses

d, the product of the two masses

The gravitational force between two masses is proportional to a. the square of the distance between the two masses b. the square of the product of the two masses c. the distance between the two masses d. the product of the two masses

c, quadruples

Two masses attract each other gravitationally. If the distance between their centers is cut in half, the gravitational force a. is cut to 1/4 b. doubles c. quadruples d. is cut in half

c, centripetal

What type acceleration does an object moving with constant speed in a circular path experience? a. linear acceleration b. constant acceleration c. centripetal acceleration

b, is directed toward the center of the circular path.

When an object experience experiences uniform circular motion, the direction of the acceleration is a. is directed away from the center of the circular path b. is directed toward the center of the circular path. c. in the same direction as the velocity vector. d. in the opposite direction of the velocity vector.

c, is directed toward the center of the circular path

When an object experiences uniform circular motion, the direction of the net force is a. is directed away from the center of the circular path b. in the same direction as the motion of the object c. is directed toward the center of the circular path d. in the opposite direction of the motion of the object

e, I , II, and III

Which equations can be used to describe the motion of an object moving in a horizontal circle with a radius R, period T and constant speed v? a. I only b. II only c. III only d. I and II only e I, II, and III

d, Issac Newton

Which famous scientist is responsible for discovering the force of attraction between two masses. a. Albert Einstein b. Nicolai Tesla c. Galileo d. Issac Newton

a, 28 days

Which of the following is best approximation of the Moon's orbital period about the earth? a. 28 days b. 24 hours c. 365 days d. none of the above; the Moon doesn't orbit the earth.

c, the mass of the satellite

Which of the following quantities is fairly inconsequential in calculating the orbital speed of a satellite around the Earth? a. the orbital radius of the satellite b. the mass of the Earth c. the mass of the satellite d. the Universal Gravitational Constant e. none of the above; they all matter