2018 #1 Free Response Question - AP Physics 1 - Exam Solution

What is the primary force acting on a spacecraft in a circular orbit around Earth?

• Normal force

• Frictional force

• Gravitational force

• Applied force

When deriving the orbital period of a spacecraft in a circular orbit, which principle is applied first?

• Conservation of energy

• Newton's Second Law (sum of forces equals mass times centripetal acceleration)

• Kepler's Third Law

• Conservation of momentum

Under what conditions is the formula Fg = mg typically used to calculate the force of gravity?

• When an object is in a circular orbit around a planet.

• When an object is in a constant gravitational field, such as on the surface of a planet.

• When an object is moving at a constant velocity in space.

• When an object is accelerating due to thrust in space.

Which of the following equations correctly represents the orbital period (T) of a spacecraft of mass 'm' orbiting Earth (mass M_E) at a radius 'R', where G is the universal gravitational constant?

• T = 2πR / v_t

• T = √(4π²R³ / (GM_E))

• T = GM_E / R²

• T = m * v_t² / R

Which of the following variables does the orbital period of a spacecraft NOT depend on, according to the derived equation?

• Mass of the Earth

• Radius of the orbit

• Gravitational constant

• Mass of the spacecraft

A spacecraft with mass 'm' orbits a planet with a period 'T'. If a second spacecraft with mass '2m' is placed in a circular orbit with the same radius, how does its orbital period compare to 'T'?

• Greater than T

• Less than T

• Equal to T

• Depends on the planet's mass

A spacecraft moves from a smaller circular orbit to a larger circular orbit. A student incorrectly reasons that if the angular position change over time remains constant, then the tangential speed of the spacecraft should increase because the radius increased. What is the flaw in this student's reasoning?

• The angular position change over time does not remain constant.

• Tangential speed is inversely proportional to the radius.

• Angular velocity is directly proportional to the radius.

• The mass of the spacecraft affects its speed.

When a spacecraft moves into a new circular orbit with a larger radius, how does its orbital speed change compared to its original speed?

• It becomes greater than the original speed.

• It becomes less than the original speed.

• It remains equal to the original speed.

• It depends on the spacecraft's mass.