Question

A fly has a mass of 1 gram at rest. how fast would it have to be traveling to have the mass of a large suv, which is about 3000 kilograms?

Answer 1

We solve this using special relativity. Special relativity actually places the relativistic mass to be the rest mass factored by a constant "gamma". The gamma is equal to 1/sqrt (1 - (v/c)^2). 

We want a ratio of 3000000 to 1, or 3 million to 1. 

Therefore:
3E6 = 1/sqrt (1 - (v/c)^2) 
1 - (v/c)^2 = (0.000000333)^2 
0.99999999999999 = (v/c)^2 
0.99999999999999 = v/c 
v= 99.999999999999% of the speed of light ~ speed of light
v = 3 x 10^8 m/s