Gravity and Force
G
6.67 x 10^(-11)
2 kg
A Moon rock has a mass of 2 kg. What is the mass of the same rock when brought to Earth?
The gravitational attraction exerted by Mercury on a spacecraft
The mass of mercury was determined by...
7 times larger
Two planets have identical diameters but differ in mass by a factor of 49. The more massive planet therefore has an escape velocity __________ than the other.
8.2 minutes
Use the Sun's distance of 150 million kilometers to calculate how long light takes to travel from the Sun to the Earth. (Note: provide the answer to two significant figures)
uniform motion
constant speed and constant velocity
balanced forces
no change in motion
retrograde motion
planets appear to speed up or slow down as they move through the ecliptic, and some go backwards! Mars does this
Kepler's 1st Law
the orbit of a planet is an ellipse with the Sun at one of the two foci
escape velocity of the earth
11 km/s
g
9.8 m/s^2
The escape velocity equals 24.2 m/s, which is smaller than the speed of the pitch. Thus the ball can escape.
A good baseball pitcher can throw a ball at 98 miles/hour (about 43.8 meters/sec). If the pitcher were on the fictional asteroid Cochise, could the pitcher throw the ball fast enough so it would escape from Cochise? Assume Cochise is a sphere and that its mass is M = 9.60 × 10^15 kg and its radius is 2.2 km = 2.20 × 10^3 meters.
29.4
A man weighs 180 lb on Earth. Calculate his weight on the Moon. Assume gravity on the moon is 1.6 m/s^2.
The action of the propellant accelerating down, giving a reaction force to the rocket.
A rocket blasts propellant out of its thrusters and "lifts off," heading into space. What provided the force to lift the rocket?
Red-shifted spectral lines.
A star moving away from the Earth at high speed will show:
4000 K
Aldebaran is a bright red star. Assuming that the star's color is the result of blackbody radiation, we conclude that the star's surface temperature is approximately .
the same as earth; the same as earth
An astronaut has a mass of 60 kilograms before she takes off in her ship. When she reaches Earth orbit, her mass is________; when she lands on the Moon, her mass is _____________
V = 2.33 X 10^5 m/s Time = 2.09 X 10^8 years
Assuming that the mass of the Milky Way Galaxy is 1011 times that of the Sun and that the Sun is 2.45 × 1020 meters from its center, what is the Sun's orbital speed around the center of the Galaxy? How long does it take the Sun to orbit the Milky Way? (In this problem, we assume that the Galaxy can be treated as a single body. Strictly speaking, this isn't correct, but the more elaborate math needed to calculate the problem properly ends up giving almost the same answer.)
Vesc = 25,100 mph
Calculate the escape velocity from the Earth in miles per hour, given that the mass of the Earth is 5.98 × 1024 kg and its radius 6.38 × 106 m. In this problem, round off G to 6.67 × 10−11 m3/(kg·s2).
Vesc = 11.2km/s
Calculate the escape velocity from the Earth, given that the mass of the Earth is 6.0 ×1024 kg and its radius 6.4 × 106 m. In this problem, round off G to 6.7 × 10−11 m3/(kg·s2).
Vesc = 620 km/s
Calculate the escape velocity from the Sun, given that its mass is 2.0 × 1030 kg and its radius is 7.0 × 108 meters.
Vesc-Moon Vesc-Earth = 0.21
Calculate the ratio of the escape velocities from the Moon and Earth. (Note: Earth's mass is about 81 times that of the Moon and its radius is about 3.8 times the Moon's radius.)
The Earth's surface gravity is about 2.530 times Jupiter's. The Earth's surface gravity is about 0.064 times Pluto's.
Compare the surface gravity of the Earth with the surface gravity of Jupiter and Pluto. If the mass of the Earth is 1.00 then the relative mass of Jupiter is 317.9 and the relative mass of Pluto is 0.0021. If the relative radius of the Earth is 1.00 then the relative radius of Jupiter is 11.21 and the relative radius of Pluto is 0.181.
Newton's Law of Universal Gravity
Every object in the universe attracts every other object
weight on earth
F=mg
Newton's 3rd Law of Motion
For every action there is an equal and opposite reaction
Newton's 2nd Law of Motion
Force = mass x acceleration
* a force is acting on it. *it is accelerating
If an object moves along a curved path at a constant speed, you can infer that (Select all that apply)
5
If the Earth were 25 times as far from the Sun as it is, the Earth's orbital velocity would be times slower.
decreased; 9
If the distance between two bodies is increased by a factor of 3, the gravitational force between them is _____ by a factor of _____
3a F = ma a = F/m
If you apply a force F to an object of mass m, it results in an acceleration a. What acceleration would result if you applied a force of 6F to an object of mass 2m? Please enter numeric part of the answer as a fraction.
The star and Earth are becoming closer together
In the spectrum of a star, the red line of hydrogen that is known to occur at 656 nm line appears shifted to 654 nm. Which of the following statements regarding the relative position of the star is correct?
Newton's 1st Law of Motion
Inertia
lower than
Mars completes one orbit around the Sun in approximately two Earth years. Mars orbits at an average distance to the Sun of about 1.5 AU, and Mars' mass is about 1/10 of the Earth's mass. Therefore, Mars' orbital speed is ________ the orbital speed of the Earth.
a physical reason for
Newton's work added ________ Kepler's laws
Star Y surface temperature is lower than 6,000 K
Star X has a surface temperature of 6,000 K, and appears yellow. Star Y appears red. What can we conclude about Star Y?
Its surface temperature is higher than 6,000 K.
Star X has a surface temperature of 6,000 K, and appears yellow. Star Y appears white. What can we conclude about Star Y?
11 km/s
Starship I weighs 2 tons and requires a speed of about 11 km/s to escape from the Earth. The escape velocity from Earth of Starship X that weighs 4 tons is.
22 km/s
Suppose that a planet was discovered that has 4 times the mass of the Earth, and the same diameter as Earth. Assume that for Earth the escape velocity is 11 km/s. What would be the escape velocity for this planet?
8.7 minutes
Suppose you are operating a remote-controlled spacecraft on Mars from a station here on Earth. How long will it take the craft to respond to your command if Mars is at its nearest point to Earth? Use data in the appendix for your calculations and round to 2 significant digits.
At the poles
The Earth's shape is somewhat flattened, so that the diameter through the poles is shorter than the diameter of the equator. Where would you weigh more?
true
The strength of the gravitational force exerted by the Sun on the Earth is the same as the strength of the gravitational force exerted by the Earth on the Sun.
482 C; 755 K
The surface temperature of Venus is about 900 degrees Fahrenheit. Express this temperature in degrees Celsius and in Kelvin.
4.3 km/s
Two spaceships are ready to lift-off from the surface of Mercury. Spaceship I requires a speed of 4.3 km/s to escape from Mercury. Spaceship II is twice as heavy as spaceship I. How much speed is required for spaceship II to escape from Mercury?
Conservation of energy
When the electron in the hydrogen atom absorbs a certain amount of energy it moves to a higher energy state. The electron could move back to its original state by emitting the same amount of energy. The amounts of energy absorbed and emitted are equal as a result of: .
7.1 ; Saturn
Which body has a larger escape velocity, Mars or Saturn? In the table below, you can find values for Mars and Saturn's radii and masses in terms of Earth's. Name Radius (Earth units) Mass (Earth units) Mars 0.532 0.107 Saturn 9.45 95.16 Vesc-Saturn Vesc-Mars = _______ so ____ has a larger escape velocity.
A. An apple that is just falling off a tree branch B. An apple that was just thrown downward from the top of a tree C. An apple that was just thrown upward from the ground ****D. All accelerate at the same rate
Which of the following apples is accelerating most?
*A car skidding on a slippery road *A brick sitting on a tabletop *Whipping a tablecloth out from under the dishes set on a table *The oil tanker Exxon Valdez running aground
Which of the following demonstrate the property of inertia? Select all that apply.
infrared
Which of the following electromagnetic waves has a wavelength longer than 800 nanometers?
Radio Waves, Infrared, Visible light, Ultraviolet, X-rays
Which of the following lists electromagnetic waves in increasing order of frequency?
X-rays, Ultraviolet, Visible light, Infrared, Radio Wave
Which of the following lists electromagnetic waves in increasing order of wavelength?
Microwave, Infrared, Visible light, Ultraviolet, X-rays
Which of the following lists the photons in increasing order of energy?
Emission lines characteristic of the atoms/molecules in the gas
Which of the following spectra will result from a hot tenuous gas?
*There is no net force on the truck. *The truck obeys Newton's 2nd law. *The truck is not accelerating.
Which of the following statements apply to a truck that is moving up a steep, straight hill at a constant speed of 10 km/hour. Select all that apply.
The net force on the puck is zero.
Which of the following statements is true about a hockey puck moving on ice in a straight line at constant speed?
The composition of a solid can be determined by examining the continuous spectrum.
Which of the following statements regarding spectra is not correct?
76
You are working at the hockey rink and your resurfacing machine breaks down in the middle of the ice. Assuming you can get it moving, how much force will you need to apply to accelerate it from rest to a speed of 1.0 m/sec in 25 seconds if it has a mass of 1,900 kg? Remember to use correct significant figures.
Kepler's 2nd Law
a line segment joining a planet and the sun sweeps out equal areas during equal intervals of time
perihelion
closest approach to sun; planet has fastest speed here because it covers the most distance at quickest amount of time
eccentricity
e=c/a; describes how much an ellipse deviates from the circle (if e = 0, then its a circle)
apehelion
farthest point from sun on orbit
Kepler's 3rd Law
p^2=a^3; true for all planets
ellipse
the curve for which the sum of the distances from the foci is constant
escape velocity
to overcome a celestial objects gravitational force and escape into space, a mass must obtain a critical speed
