What are two ways in which comets are different from other celestial bodies?

a. nucleus is rocky, with dust and ice; often found between mars and jupiter
b. nucleus is a gas ball; usually come from far away from the sun
c. nucleus of dust, rocks, and ice; may have a long, gaseous trail
d. called a meteor as soon as it develops the long gaseous tale; may have an orbit that takes more than 100 years to complete

The mass of a muon is 207 times the electron mass; the average lifetime of muons at rest is 2.21 μs. in a certain experiment, muons moving through a laboratory are measured to have an average lifetime of 7.04 μs. for the moving muons, what are (a) β (b) k, and (c) p? the rest energy of the electron is 0.511 mev.

Moon effect. some people believe that the moon controls their activities. if the moon moves from being directly on the opposite side of earth from you to being directly overhead, by what percentage does (a) the moon's gravitational pull on you increase and (b) your weight (as measured on a scale) decrease? assume that the earth–moon (center-to-center) distance is 3.82 × 10^8 m, earth's radius is 6.37 × 10^6 m, moon's mass is 7.36 × 10^22 kg, and earth's mass is 5.98 × 10^24 kg.

Iwill give 30 points to whoever answers ! what is the formula for actual mechanical advantage and ideal mechanical advantage?