ASTRO CH 3: Laws of Motion

In which of the following situations would the object be experiencing an unbalanced force? a. car moving at a constant speed and direction due east b. car moving at constant speed turning a corner c. rocket moving at a constant speed straight up away from Earth d. truck at rest

b. car moving at constant speed turning a corner

If the distance between Earth and the Sun were cut in half, the gravitational force between these two objects would a. decrease by a factor of 4. b. increase by a factor of 4. c. increase by a factor of 2. d. decrease by a factor of 2.

b. increase by a factor of 4 (when distance decreases, force increases by the inverse square of that)

In the following figure, if the woman pushes with a force of 200 newtons (N) and the container is 100kg, what will be the acceleration of the container? Assume negligible friction between the cart and floor. a. 0.5 m/s^2 b. 1 m/s^2 c. 2 m/s^2 d. 0.75 m/s^2

c. 2 m/s^2 a=F/m=200kg m/s^2 / 100 kg= 2 m/s^2 *1 N= 1 kg m/s^2

If an object is moving in a circular orbit at a constant speed, which of the following is true? a. There is no force acting on it. b. Its velocity is constant. c. It accelerates. d. Its acceleration is zero.

c. It accelerates (because its velocity changes)

What is true about a circular orbit? a. It's the fastest speed of all possible orbits. b. Speed varies. c. Speed must be constant. d. It exceeds the escape velocity.

c. Speed must be constant

What is true about an elliptical orbit? a. It exceeds the escape velocity. b. Speed must be constant. c. Speed varies. d. It is unbound

c. Speed varies.

The Earth is closest to the Sun in January and farthest from the Sun in July. When is the Earth moving the fastest in its orbit? ( January / July )

January because the Earth is closest to the Sun.

Does Kepler's first law allow for a circular planetary orbit? ( Yes / No )

No, Kepler's first law explains that planetary orbits aren't perfectly circular but that the orbits are actually ellipses.

The observation of a gibbous _______________ through the telescope proved that the Ptolemaic model was incorrect.

phase of Venus

Ptolemy used epicycles in his model to describe ______________________ motion.

retrograde

_____________________ was the first to use the telescope to view sky objects.

Galileo

Object A and Object B initially have the same mass. If Object A's mass increased, what would happen to the gravitational force between the two masses? ( The force would decrease. / The force would increase. )

If Object A's mass increased, the gravitational force between the two masses would increase.

Object A and Object B have the same mass. If the distance between the two objects increased, what would happen to the gravitational force between the two masses? ( The force would decrease. / The force would increase. )

If the distance between the two objects increased, the gravitational force between the two masses would decrease.

The semimajor axis of Earth's orbit is 1 AU. The semimajor axis of Saturn's orbit is 9.5 AU. Which planet has a longer orbital period? ( Earth / Saturn )

Saturn had a longer orbital period because its semimajor axis is greater than that of Earth, so it has to travel more with a slower speed to complete its orbit.

Heliocentric means ____________________________.

Sun is at the center of the solar system and that all the planets orbit it.

_________________________________ measured the positions of the known planets using naked eye observations—his data was sought by Kepler.

Tycho

The acceleration due to gravity on the Moon is 1/6 g. The acceleration due to gravity on Mars is 1/3 g. On which of these worlds would you weigh more? ( Mars / Moon )

You would weigh more on Mars because Mars would take ⅓ of your weight on Earth while the Moon would only take ⅙ of your weight on Earth.

If your weight on the Moon is 1/6 your weight on Earth, what is the acceleration caused by gravity on the Moon? a. 1.60 m/s2 b. 0.17 m/s2 c. 58.8 m/s2 d. 9.8 m/s2

a. 1.60 m/s^2

As the astronaut depicted here pushes a wrench away from himself, which arrow best describes the acceleration acting on him? [ a is a smaller force pointing left, d is slightly larger than a and points right, b is a big force pointing left, c is the same size as b but points right ] a. a b. b c. c d. d

a. a (because since the astronaut weighs more, it will accelerate less because acceleration and mass is inversely proportional) F=ma; a=F/m

Which of the following ellipses has the largest eccentricity? [ a has very big distance between foci and looks oblique; b has smaller distance between foci than a; c has smaller distance than b; d is a circle ] a. a b. b c. c d. d

a. a (larger distance between foci = bigger eccentricity)

According to the inverse square law, what is the impact on the force of gravity between two masses if their separation is doubled? The a. force is quartered. b. force is halved. c. force doubles. d. force quadruples.

a. force is quartered (when separation increase, force decreases by inverse square of that)

What force holds planets in their orbits? a. gravity b. air resistance c. electromagnetic d. friction

a. gravity

What must an object be doing to be considered in orbit around the Earth? a. in a state of constant free fall around the Earth b. escaping gravity c. constantly moving away from Earth d. constantly propelled

a. in a state of constant free fall around the Earth

The sloshing of coffee in a cup as a car slows down, speeds up, or turns is due to a. inertia. b. the coffee's weight. c. the contact forces between the molecules of the material. d. the force of gravity.

a. inertia.

The force of gravity exerted on an object is directly related to its a. mass. b. size. c. density. d. inertia.

a. mass

If your weight on Earth was 500 N, what would your weight be on the Moon? a. 500 N b. 83 N 250 N 125 N

b. 83 N (500N / 6)

Which scientist ended up under house arrest because of his support of the heliocentric model? a. Tycho Brahe b. Galileo Galilei c. Johannes Kepler d. Isaac Newton

b. Galileo Galilei

If the distance between Earth and the Sun were doubled, the gravitational force between these two objects would a. increase by a factor of 2. b. increase by a factor of 4. c. decrease by a factor of 4. d. decrease by a factor of 2

c. decrease by a factor of 4.

Which of the following could be observed without the use of a telescope? a. Jupiter's moons b. spots on the Sun c. retrograde motion of the planets d. phases of Venus

c. retrograde motion of the planets

Which of the following properties of an astronaut changes when he or she is standing on the Moon, relative to when the astronaut is standing on Earth? a. all choices are correct b. inertia c. weight d. mass

c. weight

In the absence of air friction, a 0.001-kg piece of paper and a 0.1-kg notebook are dropped and allowed to fall to the ground. How do their accelerations compare? a. The paper's acceleration is 100 times faster than the notebook's acceleration. b. notebook's acceleration is 100 times faster than the paper's acceleration. c. notebook's acceleration is 1,000 times faster than the paper's acceleration. d. accelerations are the same.

d. accelerations are the same

Once a satellite's velocity at closest approach equals or exceeds the __________ velocity, it is in an unbound orbit. a. tangential b. circular c. linear d. escape

d. escape

Your weight is directly proportional to your a. age. b. height. c. altitude. d. mass.

d. mass

Which observations made by Galileo are inconsistent with the geocentric model of astronomy? a. sunspots b. retrograde motion of Mars c. craters on the Moon d. orbits of Jupiter's moons and phases of Venus

d. orbits of Jupiter's moons and phases of Venus

Which of the following pair of orbital parameters appear in Kepler's third law? a. eccentricity and the period b. the period and the semiminor axis c. eccentricity and the semimajor axis d. the period and the semimajor axis

d. the period and the semimajor axis

What type of orbit results when a satellite has a velocity greater than the escape velocity? a. circular b. linear c. bound d. unbound

d. unbound

Inverse Square Law for Gravitation

the gravitational attraction force is inversely proportional to the square of their separation distance