# 30,000 fleas jumping off an elephant

**1. The problem statement, all variables and given/known data**

A flea infested elephant with a mass of 3500 kg is standing on a frozen lake wearing frictionless ice skates. If 30000 fast fleas jump off the elephants back (in a horizontal direction) per second, and each flea jumps with a velocity of 10 m/s find the velocity of the elephant using conservation of momentum. Each flea has a mass of 10 milligrams

**2. Relevant equations**

v2 = 2m1/(m1+m2)

**3. The attempt at a solution**

I converted 10 milligrams to kg and multiplied by 30,000 and got .3 kg. I imagined this as an elastic collision of a .3 kg object hitting the elephant at 10 m/s. So, solving for the elephants final velocity.

v2 = 2(.3)/ (3500+.3)

v2 = .6/(3500.3)

v2 = 1.7 x 10^(-4) m/s

is this correct?

http://ift.tt/1rWmbFk

## Leave a comment