The moon has a mass of 7.4 × 1022 kg and
Completes an orbit of radius 3.8×108 m about
Every 28 days. The Earth has a mass of
6 × 1024 kg and completes an orbit of radius
1.5 × 1011 m every year.
What is the speed of the Moon in its orbit?
Answer in units of m/s.


What is the kinetic energy of the Moon in
Orbit?
Answer in units of J.


What is the kinetic energy of the Earth?
Answer in units of J.

Quote:

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Originally Posted by eal0088

The moon has a mass of 7.4 × 1022 kg and
completes an orbit of radius 3.8×108 m about
every 28 days. The Earth has a mass of
6 × 1024 kg and completes an orbit of radius
1.5 × 1011 m every year.
What is the speed of the Moon in its orbit?
Answer in units of m/s.


What is the kinetic energy of the Moon in
orbit?
Answer in units of J.


What is the kinetic energy of the Earth?
Answer in units of J.

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velocity is distance per time

v=d/t

The distance the moon travels is the circumference of the circle it makes

d=c=2*pi*r
d= 2*pi*3.8×10^8m
d= 2.39*10^9 meters

time is given as 28 days, we need to convert it to seconds.

28 days *24 hours/day * 60 mins/hour * 60sec/min = 2419200 seconds

v= d/t = 2.39*10^9/2419200 seconds
v= 987 m/s

part two asks for the moons kinetic energy (K.E.)

KE = (1/2)*m*v^2 , where m is the mass of the object, and v is the speed it is traveling at.

KE = 0.5*7.4 × 10^22*(987)^2
KE = 3.60*10^28 Joules

Part three is similar to this, see if you can complete it from here.