Gravitation, Orbital Motion, and Energy

Kepler's first law states that the planets move in ________ orbits around the Sun. Kepler's second law states that the closer a planet is to the sun the ________ it travels.

• elliptical, faster

• elliptical, slower

• circular, faster

• circular, slower

Two satellites are in orbit around a planet. One satellite has an orbital radius of 8.0×10⁶ m. The time period of revolution for this satellite is 1.0×10⁶ s. The other satellite has an orbital radius of 2.0×10⁷ m. What is this satellite’s time period of revolution? Hint: Use Kepler's third law.

• 5.0×10⁵ s

• 4.0×10⁶ s

• 2.5×10⁶ s

• 1.3×10⁷ s

Find the value of g on the moon, if the mass and radius of the moon is 7.346×10²² kg and 1.74×10⁶ m.

• 2.622 m/s²

• 3.452 m/s²

• 1.618 m/s²

• 4.622 m/s²

Earth (m_earth = 5.97x10²⁴kg) orbits the sun (m_sun=1.99x10³⁰kg) at a mean distance of 1.50 x 10¹¹m. What is the gravitational force of the Sun on the Earth? (G=6.67x10^-11Nm²kg^-2)

• 5.29 x 10³²N

• 3.52 x 10²²N

• 5.90 x 10^-2N

• 1.77 x 10^-8

A satellite is orbiting at a distance of 408 km above the Earth. What is the orbital speed of the satellite? The mass of the Earth is  $\ 5.97\times10^{24}\$  kg and the radius of the Earth is 6,371 km. 

• 2,400 m/s

• 242,000 m/s

• 7,664 m/s

• 186,000 m/s

Which law states that every object in the universe attracts every other object in the universe?

¿Qué ley establece que todos los objetos del universo atraen a todos los demás objetos del universo?

• Newton’s first law of motion;

  La primer ley de movimiento de Newton

• Newton’s second law of motion;

  La segunda ley de movimiento de Newton

• The law of universal gravitation;

  La ley universal de la gravitación

• The law of inertia;

  la ley de la inercia

The work done by gravity on a car of mass 1000kg moving horizontally on a freeway with velocity 20m/s.

• 9800J

• Zero

• 9800N

• 20000J

Gravity acts downwards with a force of 100N on an object moving to the right on a table acted upon by a force of 150N along the table, pointing to the left. It moves thru a distance 2m. What is the work done by the net force?

• 300J

• 500J

• 200J

• -300J

The work done on a car in moving uphill equals its gravitational potential energy at the top. Assume the car goes up a constant incline, with force generated by the engine of the car with magnitude 10000N, thru a distance of 2km. What is the GPE at the top of the hill?

• 20,000J

• 200,000J

• 20,000kJ

• 200kJ

The GPE of a trolley-car on a roller coaster at the top of an incline is converted completely to kinetic energy of the trolley-car at the bottom of the incline. The mass of the trolley-car is 2000kg and it starts at a height 200m. What is the velocity of the trolley-car at the bottom of the hill. Note g=9.8m/s^2.

• 58.4m/s

• 1800m/s

• 62.6m/s

• 62.6m