If the resulting acceleration of the rat and cage is 0.35 m/s2, what is the rat's mass?

Question

A biologist is studying the growth of rats in an orbiting space station. To determine a rat's mass, she puts it in a 305 g cage, attaches a spring scale, and pulls so the scale reads 0.46 N. If the resulting acceleration of the rat and cage is 0.35 m/s2, what is the rat's mass?

Answer 1

f = ma; m = f/a
m = 0.46/0.35 = 1.314 kg
mrat = m - mcage = (1.314 - 0.305) kg
Big rat!