Our Moon:

was formed by the collision of Earth with a Mars-sized protoplanet.

was a separate small planet before it was captured by Earth's gravity.

is 93 million miles away from Earth.

is 4.3 light years away from Earth.

has a composition similar to Earth's core.


was formed by the collision of Earth with a Mars-sized protoplanet.

Physics & Space Science

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A brittle PMMA specimen that has a KIc of 0.7 MPa·m1/2 fractures at a tensile stress of 50 MPa. Observation of the fracture surface indicates that the fracture started at the specimen edge. Predict the length of the crack that initiated the fracture.

What will be an ideal response?

Physics & Space Science

How is an X-ray burst (in an X-ray binary system) similar to a nova?

A) Both involve explosions on the surface of stellar corpse. B) Both typically recur every few hours to every few days. C) Both are thought to involve fusion of hydrogen into helium. D) Both result in the complete destruction of their host stars.

Physics & Space Science

One of the most efficient engines built so far has the following characteristics: combustion chamber temperature = 1900°C; exhaust temperature = 430°C. 7 × 109 cal of fuel produces 1.4 × 1010 J of work in one hour

What is the power output, in hp, of this engine?

Physics & Space Science

You want to insert an aluminum rod, which at 20°C has a radius of 1.00020 cm into a copper tube which has a radius of 1.00010 cm at the same temperature

You decide to put both of them in the refrigerator. At what temperature will the rod just fit if both are cooled to the same temperature? The coefficient of thermal expansion for aluminum is 2.4 × 10-5K-1, and that of copper is 1.7 × 10-5K-1. A) 7.8°C B) 6.3°C C) 9.2°C D) 14.7°C E) 5.7°C

Physics & Space Science