All the statements can be used to explain about Earth's magnetic field.
Earth's magnetic field is almost same to that of the bar magnet. The magnetic field of the earth occurs from its core. It has an inner core which is solid in nature. in the outer core, there is a motion of the liquid due to heat flow from the inner core to the core mantle boundary which proves that the outer core is liquid and moving. The Earth's core consists of iron and nickel as the Eddy currents in the iron and nickel liquid helps generating the Earth's magnetic field.
Hence, all the three statements are true and can be used to explain the Earth's magnetic field.
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The acceleration of the meteoroid due to the gravitational force exerted by the planet = 12.12 m/
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Explanation:
A meteoroid is in a circular orbit 600 km above the surface of a distant planet.
Mass of the planet = mass of earth = 5.972 x
Kg
Radius of the earth = 90% of earth radius = 90% 6370 = 5733 km
The acceleration of the meteoroid due to the gravitational force exerted by the planet = ?
By formula, g = 
where g is the acceleration due to the gravity
G is the universal gravitational constant = 6.67 x

M is the mass of the planet
r is the radius of the planet
Substituting the values, we get
g = 
g = 12.12 m/
The acceleration of the meteoroid due to the gravitational force exerted by the planet = 12.12 m/
1000 miles = 1610km = 1.61x10^6m
2 weeks = 14 days = 14x24x1440
V=d/t = 1.61x10^6/14x24x1440
= 3.33m/s
A. Solid turns into a gas
Answer:4kg
Explanation:
acceleration due to gravity(g)=10m/s^2
Weight(w)=40N
Weight=mass x g
40=mass x 10
Divide both sides by 10
Mass =40/10
Mass=4kg