Gravitation Pretest

When wind applies force to a pinwheel, the arms start to move in a circular motion. Which additional forces keep the arms of the pinwheel moving in a circular motion?

• An inward pull along the arms

• An outward push along the arms

• The upward push of the support

• The downward pull of the support

A 2000 kg car travels at a constant speed of 12 m/s around a circular track with a radius of 30 meters. What is the direction of the centripetal force on the car as it goes around the curve?

• Toward the center of the circular curve

• Away from the center of the circular curve

• Opposite the direction of the car's motion

• In the direction of the car's motion

Which situation would most likely cause an object to travel in a circular motion?

• one force acting on the object in the opposite direction of the motion

• two forces acting on an object in the same direction as the motion

• one force acting on the object perpendicular to the motion

• two forces acting on the objects in the opposite direction as motion

As represented in the diagram below, a roller coaster cart starts from rest and accelerates, due to gravity, down a track. The cart starts at a height that enables it to complete a loop in the track. The magnitude of the centripetal force keeping the cart in circular motion is greatest at which point?

• J

• K

• L

• M

The diagram represents a ball traveling with a uniform clockwise circular motion on a string. Which of the following best represents the directions of both the velocity and centripetal acceleration of the ball at the instant shown in the diagram?

• 
• 
• 
• 

A turn on a racetrack is 915 meters long and can be considered a semicircle with a radius of 291 meters, as shown in the diagram. What is the centripetal acceleration of a car that completes the semicircular turn at a constant speed of 15 seconds?

• 0 m/s²

• 3.14 m/s²

• 12.8 m/s²

• 61.0 m/s²

The center of a 910 kg satellite is 9.9x10⁶ from earth's center. What is the gravitational force between the satellite and Earth?

• 4.5 x10³ N

• 3.7 x 10³ N

• 8.9 x 10³ N

• 1.7 x 10³ N

Suppose Earth orbited a star whose mass was double the mass of the sun. If the radius of Earth's orbit remained the same as it is now, then compared with the gravitational force between Earth and the sun, the gravitational force between Earth and the star would be

• half as much

• the same

• two times as much

• four times as much

The mass of the moon is 7.36 x 10²² kg, and the radius is 1.74 x 10⁶ m. What is the gravitational force of a 1.0 kg rock on the surface of the moon?

• 4.91 x 10¹² N

• 1.62 N

• 9.81 N

• 1.28 x 10²⁹ N

According to Newton's law of universal gravitation, in which of the following situations does the gravitational attraction between two bodies always increase?

• the masses increase, and the distance between the centers of mass increases.

• the masses increase, and the distance between the centers of mass decreases

• the masses decrease and the distance between the centers of mass increases

• the masses decrease and the distance between the centers of mass decreases