Unit 7 Test Flashcards
Evaluate the following statement as true or false. If a person could carve out the exact center of the Earth and station himself there, the person would be weightless. Assume the Earth is spherical and has a uniform density.
true
The gravitational force between two objects has a magnitude of F. If both masses were doubled and the distance between them doubled, the new force would have which of the following magnitudes?
F
Which of the following is the gravitational force between the Earth and the Moon? The Earth’s mass is 610^24 kg and the moon’s mass is 7.410^22 kg, and the distance between their centers of mass is 3.8*10^8.
2.1*10^20 N
Which of following is the resultant gravitational force acting on the 100 kg mass in the diagram?
1.56*10^-6 N
A rocket leaves the surface of the Earth and flies to a distance of one Earth radius above the surface of the Earth. What happens to both the gravitational force and potential energy of the rocket?
The force decreases by factor of 4. The potential energy increases by factor of 2.
The radius of the Moon is known to be 1.7 × 10^6 m. Astronauts who walked on the Moon measured the time it takes an object to fall 1 m on the Moon to be about 1.1 s. Using this information, which of the following is the mass of the Moon?
7.1 × 10^22 kg
Which of the following is the resultant gravitational force vector acting on the 100 kg mass at the origin of the diagram?
1.3*10^-3 N at -85 degrees
NASA wants to launch a new satellite that will remain in a circular orbit 300 km above the surface of the Earth. Determine the orbital speed necessary for the satellite to remain in this orbit if the mass of the Earth is 5.97 × 1024 kg and its radius is 6.38 × 10^6 meters.
7720 m / s
Using Kepler’s third law of planetary motion, how many times larger is the average radius of Neptune’s orbit if it takes 164 Earth-years to orbit the Sun? Approximate each orbit as being circular.
30 times larger
Recently it was discovered that a planet with mass 1.3 × 1028 kg orbits the star 70 Virginis, which is 59 light years from the Earth. 70 Virginis has approximately the same mass as the Sun, at 1.9 × 1030 kg. If the planet is in a nearly circular orbit of radius 7.1 × 1010 m what is the period of the planet in terms of Earth-days?
122 days
A 3000 kg satellite is in a circular orbit around the Earth. The radius of the orbit is r0. Using the energy diagram, what is the value of r0? The mass of the Earth is 6 × 1024 kg.
6.0 × 10^7 m
A binary star system consists of two identical stars moving in circular orbits around the system’s center of mass (see the diagram). The mass of each star is M and the radius of the orbit is R. Which expression correctly gives the orbital speed for one of the stars?
(GM/4R)^1/2
A binary star system consists of a star of mass M and a second star of mass 3M. They orbit in circular paths around their common center of mass with radii ra and rb, respectively (see the diagram). Which expression below is correct for the speed of the larger star, vb?
(GMrb)^1/2 / (ra + rb)
Evaluate the following statement as true or false. Kepler’s first law of planetary motion states that the Sun is at the center of a planet’s elliptical orbit.
false
True or false?
Assume the average person walks with a speed of 1.5 m / s. The asteroid Dactyl has a radius of roughly 700 m and a mass of 3.6 × 102 kg. An average person walking on Dactyl would be able to escape Dactyl’s gravity and “walk” off into space.
true
