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# S18 Ph 121 Chaper 13 Practice 2

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## Richard Datwyler

on 17 July 2018

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#### Transcript of S18 Ph 121 Chaper 13 Practice 2

Chapter 13 Practice 2
Orbits and Energy

A starship is circling a distant planet of radius R. The astronauts finds that the free-fall acceleration at their altitude is half the value at the planets surface. How far above the surface are they orbiting?
.41 R
A projectile is shot straight up from the earth's surface at a speed of 10,000 km/h. How high does it go?
394 km
418 km
(compare to flat earth)
What then is the escape velocity from earth?
11,191 m/s
the moon?
Jupiter?
60,217 m/s
2,375 m/s
Sun?
617,590 m/s
Nothing can escape the event horizon of a black hole, not even light. You can think of the event horizon as being the distance from a black hole at which the escape speed is the speed of light, 3.00 × 10 m/s, making all escape impossible. What is the radius of the event horizon for a black hole with a mass 6.5 times the mass of the sun? This distance is called the Schwarzschild radius.
8
19,173 m
The asteroid belt circles the sun between the orbits of Mars and Jupiter. One asteroid has a period of 5.0 earth years.
What is the asteroid's orbital radius?
What is the asteroid's orbital speed?
4.37 x 10^11 m
17,400 m/s
Three satellites orbit a planet of radius R, as shown in the figure. Satellites S1 and S3 have mass m. Satellite S2 has mass 2 m. Satellite S1 orbits in 280 minutes and the force on S1 is 10,000 N. What are all the periods and forces on the other satellites?
280 m 514 m
20,000 N 4,440 N
Two Jupiter-size planets are released from rest 1 x 10^11 m apart. What are their speeds as they crash together?
30,000 m/s
torque
angular momentum
rotational energy
center of mass
angular kinematics
angular dynamics
moments of inertia
Statics

Gravitational force
Gravitational acceleration
Gravitational energy
orbits

Numerics
Can we do Question one from mastering physics? I haven't been able to figure out what I'm doing wrong.
Planet Z is 6000 km in diameter. The free-fall acceleration on Planet Z is 10.0 m/s2 .
What is the free-fall acceleration 1.00×104 km above Planet Z's north pole?
.53 m/s^2
1.3 x 10^24 kg
How can something have negative energy?
What is the difference between orbital and escape velocity?
could you explain periods of orbit a bit more.
What is the ratio of the sun's gravitational force on you to the earth's gravitational force on you?
.0006
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