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**One way to attack a satellite in Earth's orbit is to launch a swarm of pellets in the same orbit as the satellite but in the opposite direction. Suppose a satellite in a circular orbit 500 km above Earth's surface collides with a pellet having mass 4.0 g.**

a.) What is the kinetic energy of the pellet in the reference frame of the satellite

b.) What is the ratio of this kinetic energy to the kinetic energy of a 4.0 g bullet from a modern army rifle with a muzzle velocity of 950 m/s?

a.) What is the kinetic energy of the pellet in the reference frame of the satellite

b.) What is the ratio of this kinetic energy to the kinetic energy of a 4.0 g bullet from a modern army rifle with a muzzle velocity of 950 m/s?

So for the kinetic energy, K = (1/2)m(v^2). I know that you need to find the velocity for that orbit's radius, therefore, I've done: Net Force = ma --> ((Gm1m2)/(r^2)) = m2((v^2)/r). With r = Radius of the Earth + 500 km --> ((6.37 x 10^6) + (5 x 10^6)). From there, I solved for the velocity and came up with (numerous times) = 7620 m/s. Then the kinetic energy, with 'm' being .004 kg, =116129 J. Which is the wrong answer.

So...moving on to part B with the wrong answer in part A didn't make much sense. I just don't quite know what I've done wrong. I know what the right answers are ( a. (4.6 x 10^5) J, b. 260. ), I just can't seem to get to them.

Any suggestions?