# Homework Help: Proper time and formulas without numbers?

1. Jun 9, 2012

### sydboydell31

Proper time and formulas without numbers???

(a) Write down the definition of proper time and explain how to use the appropriate formula with an example.

(b) Write down the definition of proper length and explain how to use the appropriate formula with an example.

(c) At what relative speed does a clock move if it runs at a rate that is one-half the rate of a clock at rest?

(d) At what relative speed does a meter stick move if its length is observed to shrink to 0.25 m?

(e) Two spaceships approach each other, each moving with the same speed as measured by a stationary observer on the Earth. Their relative speed is 0.70c. Determine the velocities of each spaceship as measured by the stationary observer on Earth.