Chapter 13 physics
Calculate the force of gravity between Earth and the moon.
2.1 x 10^20 N
Calculate the force of gravity between Earth. (mass = 6.0 1024 kg) and the moon (mass = 7.4 1022 kg). The average Earth- moon distance is 3.8 108m.
2.1 x 10^20 N
Calculate the force of gravity between a new born baby (4 kg) and Mars (6.4 x 10^23) when Mars is closest to Earth. (8 x 10^10 m)
2.7 x 10^-8 N
Calculate the force of gravity between Earth and the sun.
3.6 x 10^22 N
What is the gravitational force between two 1 kg bodies that are 1 m apart?
6.67 x 10^-11 N
Gravitational force acts on all objects in proportion to their masses. Why, then, doesn't a heavy object fall faster than a lighter one?
Acceleration of the fall = force per mass, which is the same for all objects.
At what distance away from Earth is the gravitational force on and object 0?
At no distance from Earth; gravitational force approaches 0 with great distances, but never actually reaches 0.
Irene says that Earths force of gravity is stronger on a piece of iron than on a piece of wood of the same mass. Do you agree? Defend your answer.
Disagree; the law of gravity states that the gravitational force on objects of equal masses at the same location is the same.
Calculate the force of gravity on a 1 kg mass at Earths surface. The mass of Earth is 6 x 10^24 kg, and its radius is 6.4 x 10^6 m.
F=Gm1m2Id^2 (6.67 x 10^-11 Nxm^2/kg^2)(1 kg) x (6 x 10^24 kg)/(6.4 x 10^6 m)^2 =9.77 N
Calculate the force of gravity on the same 1 kg mass if it were 6.4 x 10^6 m above Earth's surface.
F=Gm1mI(2d^2)=9.8 N/4 = 2.44 N
What was the cause of pertubations discovered in the orbit of Planet Uranus?
Gravity from Neptune
What two competing effects determine the size of a star?
High pressure from the hot interior pushes outward and the gravitation pulls inward. When both are in balance, the size of the star is established.
If the gravitational forces of the sun or the planets suddenly disappeared, in which line of path would the planets move?
In a straight line
How does the force of gravity depend in the distance between 2 objects?
Inversly as the square of the distance between their centers.
Would the gauge inside a bathroom scale be more compressed if you weighed yourself in an elevator that accelerated upward? Downward?
More compressed Less compressed
Stepan says that the force of gravity is stronger on a piece of papwr after it's crumpled. His classmates disagree do Stephan "proves" his point by dropping two pieces of paper, one crumpled and the other one not. The crumpled piece falls faster. Has Stephan proved his point? Explain
No; the gravitational force is the same on the two pieces of paper of equal mass. The crumpled piece falls faster due to the reduced air resistance, not to an increased gravitational pull.
Earth and the moon are gravitationally attracted to each other. Does the more massive Earth attract the moon with a greater force, the same force, or less force than the moon attracts Earth.
Same
How dies the tangential velocity if a planet relate to it orbiting around the sun?
Tangential velocity must be great enough so that the planet falls around, rather than into the sun.
How does the force of gravity between bodies change when the distance between them is doubled?
The force hs 1/4 as much in accord with the inverse square law.
In what sense does the moon "fall"?
The moon falls beneath the straight line it would follow if there were no forces acting on it.
A friend proposes an idea for launching space probes that consists of boring a hole completely through Earth. Your friend reasons that a probe dropped into such a hole would accelerate all the way through and shoot like a projectile out the other side. Defend or oppose the reasoning of your friend.
The probe will accelerate only toward the center, and then decelerate until it reaches the far end. It will simply oscillate back and forth.
The planet Jupiter is about 300 times as massive as Earth, but an object on its surface would weigh only 2.5 times as much as it would on Earth. Can you come up with an explanation? (Hint: Let the terms in the equation for gravitational force guide your thinking.)
The radius of Jupiter is greater so there's a greater distance between the object's and Jupiter's CGs.
Why are ocean tides higher at the full moon?
The sun, the moon, and the Earth are alogned at the time, all pulling together.
Why are black holes black?
They are black because they absorb light without emitting or reflecting it. Hence they are completely dark.
Do tides depend more on gravitational pull or on the difference in strengths? Explain.
Tides depend on differences in strengths of gravitational pull. Tides are caused by elongation in the oceans.
True or false: The strength of a gravitational field eauals the gravitational force mass on a particle in the field.
True
What is the value if Earth's gravitational pull at the center of Earth?
Zero
