Are comets common? Explain why or why not

What will be an ideal response?


Yes. Faint comets are common; several dozen are discovered each year. Truly bright comets appear about once per decade. An average person might see five or ten bright comets in a lifetime. Astronomers do not know exactly how many, but there could be one hundred billion in the Oort cloud.

Physics & Space Science

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A cylindrical tank is assembled by welding steel sections circumferentially. Tank diameter is 1.5 m, thick- ness is 20 mm, and internal pressure is 2.0 MPa. The maximum shear stress in the heads is approximately:

(A) 19 MPa
(B) 23 MPa
(C) 33 MPa
(D) 35 MPa

Physics & Space Science

The longer the period of pulsation for a Cepheid, the more massive and luminous the variable giant star is

Indicate whether the statement is true or false

Physics & Space Science

The orbits of halo stars are typically circular and have a low inclination with respect to the disk

Indicate whether the statement is true or false

Physics & Space Science

Consider a 1000. Gauss magnetic field along the z axis and a proton moving with an instantaneous velocity of = 3 + 4 km/s (note its speed is 5. km/s composed of 3. km/s along the x axis and 4. km/s along the z axis)

Determine the radius of its spiraling orbit. [proton: 1.67 × 10-27 kg and 1.6 × 10-19 Coulomb]

Physics & Space Science