Lesson: Circular Motion

Topic Review:

Circular Motion

​

3-1: The Gravitational Field

• ALL objects attract each other with a force of gravitational attraction. 

• The force depends on the mass of the objects and the distance between their centers.

Multiple Choice

Force of gravity is inversely proportional to

• Mass

• Weight

• Distance

• Time

Multiple Choice

If I double the distance between two objects, what happens to their gravitational Force?

• 4x bigger
• 4x smaller
• 2x bigger
• 2x smaller

Multiple Choice

If I double the mass of one object without changing anything else, What would happen to the gravitational force between that object and any other object?

• Doubles

• Quadruples

• Cut in Half

•  $\frac{1}{4}$  as much

Multiple Choice

What happens to Gravitational force if I double both of the masses but don't change their distance?

• doubles

• half as big

• 4 times bigger

• $\frac{1}{4}$ as much or 4 times smaller

Multiple Choice

Find the distance between two objects whose masses are m₁ = 4,500 kg, and m₂ = 8,700 kg; if the gravitational force between them is F = 2.0 x 10^-8 N.

• 130565.25 m

• 361.34 m

• 0.19575 m

• 0.783 m

3-2: Angular Velocity & Centripetal Acceleration

• There are "circular" variables that correspond to linear variables.

• Change in Angle, Angular Velocity, and Centripetal Acceleration.

• There is also a Linear Velocity for objects in circular motion!

Multiple Choice

The rotational equivalent to x (displacement), v (velocity) and a (acceleration) are?

• m, m/s, m/s²

• θ, ω, α

• x, x/t, α

• μ, Σ, τ

Multiple Choice

Which of the following is NOT a unit of angular velocity?

• Meters per second

• Revolutions per minute

• Revolutions per second

• Rotations per second

Multiple Choice

A bug on a spinning record will make more turns per minute if it is located toward the center of the record.

• True

• False

Multiple Choice

Which represents the acceleration of the ball? The ball is moving counter-clockwise.

• A

• B

• C

• D

Multiple Choice

Where should you go on a merry go round to go fastest?

• Into the middle!

• Out to the edge!

• Doesn't matter- rotational speed and linear speed are the same everywhere!

• Jump up to go fastest!

3-3: Centripetal Force

• This is the name given to a force moving an object in uniform circular motion.

• ​If you lost the centripetal force the object would stop revolving and continue in a straight line tangent to the circumference of the circle.

• Time Period is the number of seconds it takes for one cycle, and the inverse is Frequency.

Multiple Choice

If mass increases force will....

• increase because they have a direct relationship

• increase because they have a inverse relationship

• decrease

• both

Multiple Choice

If radius increases force will....

• decrease because they have a direct relationship

• decrease because they have a inverse relationship

• increase

• both

Multiple Choice

If velocity increases force will....

• increase because they have a direct relationship

• increase because they have a inverse relationship

• decrease

• both

Multiple Choice

Decreasing the radius when making a turn allows you to____?

• Increase your friction
• Keep a high speed
• Change your inertia
• Decrease gravitational pull

Multiple Choice

The centripetal force of satellites is similar to gravitational force because they are both a net force towards the center of earth.

• True
• False

Multiple Choice

A dog sits 1.50 m from the center of a merry-go-round and revolves at a tangential speed of 1.80 m/s. If the dog’s mass is 18.5 kg, what is the magnitude of the centripetal force on the dog?

• 56 N

• 21 N

• 40 N

• 98 N

3.4 Applications of Circular Motion

• All planetary orbits are ellipses.

• Planets cover equal areas in equal time periods.

• Satellites move faster when closer to the sun, and slower when further away.

Multiple Choice

An ellipse is drawn around two points called

• aphelion
• perihelion
• foci
• axis

Multiple Choice

When a planet orbits the Sun, one of the foci of the elliptical orbit is 

• the axis
• the perihelion
• the center
• the Sun

Multiple Choice

The farther away a planet is from the sun, the _______ it takes it to orbit the sun once. 

• longer
• shorter

Multiple Choice

Earth will travel fastest in its orbit when

• the earth is closest to the sun (January 3rd)

• the earth is farthest from the sun (July 3rd)

Multiple Choice

The "Law of Harmonies" is which of Kepler's Laws?

• 1st
• 2nd
• 3rd
• 4th