ASTRO 7N Chapter : Astro

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poynterhannah05

8 Feb 2023

School

PSU

Department

Astronomy and Astrophysics

Course

ASTRO 7N

Professor

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Document Summary

The strength of gravity, g, on the surface of a planet is given by g=m/r2 where m is the mass of the planet and r is its radius. Note the radius is squared but the mass is not. If the mass of a planet were twice that of another, but they had the same radius, the gravity felt on the surface of the more-massive one would be twice as strong. If the radius of a planet were twice that of another, the gravity is 1/(2)2 = 1/4as strong. Putting the effects of mass and radius together, you should be able to gure out the surface gravity of mars, relative to the earth. Mars has 1/10 the mass of the earth and 1/2 the radius of earth. So for mars, g = (1/10) / (1/2) 2 = (1/10) / (1/4) = 4/10.

Related Questions

Consider a block of mass m sliding down an inclined planeandit has three forces acting on it (1) a gravitationalforce(pointing down). (2) a normal force perpendicular to thesurface ofthe plane. (3) a friction force opposing motion downtheplane.

In the case of a surface with negligible, Friction forceiszero, and there are only two external forces acting on theblock.What will the acceleration of a cart be according to thetheory-Newton's laws?

How will it compare to the magnitude of thegravitationalacceleration g?

Please put it into words.

4) According to the ancient Greeks, the Earth was the center ofthe universe and the sun, moon, stars, and planets all went aroundthe Earth. In the 1543 Copernicus proposed the heliocentric theoryof the universe in which the Earth was just another planet orbitingthe Sun and only the moon orbited the Earth.

a) What is the speed at which the Moon goes around the Earth?
b) How does the Moon's orbital acceleration compare to theacceleration of objects near the surface of the Earth?
c) What is the magnitude of the force that the Earth's gravityexerts on the Moon to keep it in orbit?
d) According to Newton's third law, all forces occur in pairs. Whatis the reaction to the Earth's gravity on the moon? Explain.

1. Which of the following describes an object with a non-zero netforce acting on it? Choose all that apply.
The moped accelerated while making a left turn.
The motorcycle traveled at a constant speed while making au-turn.
The truck slowed down while making a right turn.
The spaceship traveled at a constant speed in a straightline.
The car sped up from 50 mph to 65 mph while moving in a straightline.

2. If you observe that an object is accelerating, what should youconclude?
A non-zero net force is acting on it. Only forces causeacceleration. As such, if an object is accelerating it must bebecause a non-zero net force is acting on it.
It must be in free fall.
It must be changing direction. Acceleration is a vector and vectorshave both magnitude and direction. Thus if an object isaccelerating it must be changing direction.
The forces acting on the object must be greater than the forces theobject is exerting.
It must be speeding up. If an object is accelerating that means itis speeding up.

3. Which of the following are true according to Newton's 2nd Law?Choose all that apply.

If the acceleration is zero, then the net force is zero.
If you apply the same force to 2 objects, the one with more masswill have a greater acceleration.
If you apply the same force to 2 objects, the one with less masswill have a greater acceleration.
If two objects have the same acceleration, the one with less masswill have a larger net force exerted on it.
If two objects have the same acceleration, the one with more masswill have a larger net force exerted on it.
The larger the net force on an object is, the larger theacceleration.
The larger the net force on an object is, the smaller theacceleration.

4. A box is on the Moon. The box weighs 152 lb and is in free fall.How much force is the box exerting on the Moon and in whatdirection?

lb
Up
Down
Right
North
East
West
Left
South

5. Which of the following are the correct units for mass? Chooseall that apply.
slugs
u
kgÂ·m/s2
g
N
m/s2
oz
lb

6. If an object is traveling in a circle, which of the followingmust be TRUE? Choose all that apply.
The object is slowing down.
The object is speeding up.
The object has a net force acting on it.
The object has a constant velocity.
The object is accelerating.

ASTRO 7N Chapter : Astro

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