Circular Motion and Gravity

Cindy and Brian are playing a carnival game. The game calls for one person from the team to twirl a ball attached to a string as illustrated in the model. That person will then let go of the string. The other teammate will need to catch the ball once it is released in a basket.

Based upon your knowledge of physics, which diagram shows the predicted path of the ball when released?

• Choice A

• Choice B

• Choice C

• Choice D

Tags

NGSS.HS-PS2-1

A child got a swing set as a toddler. No matter how hard he pumped his legs, he could never make the swing circle over the top of the swing set. As he grew, his mom shortened the length of the chains holding the seat. Now he can make a 360 degree revolution over the top of the swing set. Which of the following factors contributes most to his ability to make the swing travel in a complete circular path?

• His mass is greater than it was when he was a toddler

• He is able to produce more force by pumping his legs than he could as a toddler

• The radius of the circle has decreased as a result of the shortened chains

• His height has changed his average distance from the ground

Tags

NGSS.HS-PS2-1

A child riding a merry-go-round feels a centripetal force. How would the force change if the velocity doubled (2x)?

• Decrease to one quarter (1/4)

• Decrease to one half (1/2)

• Double (2x)

• Quadruple (4x)

A car is traveling around a circular track.

If the car traveling at a velocity of 15 m/s, what is the centripetal acceleration of the car?

• 22.5 m/s², outward

• 22.5 m/s², inward

• 1.5 m/s², outward

• 1.5 m/s², inward

A car is travel clockwise around a circular track at 8 m/s. Which answer below includes the correct vectors and values for the velocity and centripetal acceleration of the car?

• Picture A

• Picture B

• Picture C

• Picture D

Tags

NGSS.HS-PS2-1

Students swing a tennis ball attached to a string in a circle. They determine the length of the string and the speed of the ball and are asked to use that information to determine the magnitude of the centripetal acceleration and to justify its vector direction. Students offer their approaches to the problem. Which student is most correct?

• Student 1:

  The centripetal acceleration can be determined by dividing the velocity by the length of the string which is like the radius of the circle. When you circle it around, it feels like the ball is pulling outward, away from the center, so the acceleration must be outward.

• Student 2:

  The centripetal acceleration could be figured out by dividing the square of the velocity by the length of the string which is like the radius of the circle. The direction of the acceleration must be pointing in toward the center of the circle since the only force acting on the tennis ball is the string, the net force is towards the center. The acceleration must be in the same direction as the net force.

• Student 3:

  The centripetal acceleration could be figured out by dividing the square of the velocity by the diameter of the circle created by the ball on the string. The direction of the acceleration must be pointing in toward the center of the circle since the only force acting on the ball is the string, making the net force directed towards the center of the circle.

• Student 4:

  Without knowing the mass of the ball, it is impossible to calculate the centripetal acceleration. I think the acceleration will be toward the center though, since the net force is also towards the center.

Tags

NGSS.HS-PS2-1

Mars has two moons. Phobos and Deimos, which both have about the same mass. The force of gravity between Mars and Phobos is much stronger than the force of gravity between Mars and Deimos. Which of the following statements is true about the two moons?

• Deimos is much closer to Mars than Phobos

• Phobos is much closer to Mars than Deimos

• The moons are the same distance away from Mars

• The gravity between the two moons makes it impossible to determine which is closer to Mars

Tags

NGSS.HS-PS2-4

A student is performing an experiment where he is able to measure the force of gravity between two masses (m₁ and m₂). Based on the data he records below, what claim can he make about how the force of gravity is related to the size of the masses? (Hint: try solving using the law of one)

• Mass one is directly proportional to the force

• Mass two is inversely square proportional to the force

• Both masses are inversely proportional to the force

• Both masses are directly proportional to the force

Tags

NGSS.HS-PS2-4

A car goes around a curve of a radius r at a constant speed v. Then it goes around the same curve at half of the original speed. Which of the following correctly identifies the change in force and the reason for it to occur? (Hint: use laws of one)

• The centripetal force increase by a factor of 2 because velocity and force are directly proportional when an object is traveling along a circular path.

• The centripetal force decrease by a factor of 4 because velocity and force have a proportional ,but squared relationship when an object is traveling along a circular path.

• The centripetal force increase by a factor of 1/2 because velocity and force have a proportional ,but squared relationship when an object is traveling along a circular path.

• The centripetal force decrease by a factor of 1/4 because velocity and force have a proportional ,but squared relationship when an object is traveling along a circular path.

Tags

NGSS.HS-PS2-1

This is considered to be a fictitious force?

• Centripetal

• Centrifugal

• Torque

• Universal Gravitation