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## Homework Statement

*A projectile is fired from a canon at a velocity of 0.4c at an elevation angle of 30° to the X-axis. An observor is moving at a velocity of 0.1c relative to the canon along the X direction.*

(a) At what angle does the observor measure the projectile to be fired?

(b) What is the projectile’s speed relative to the observor?

(a) At what angle does the observor measure the projectile to be fired?

(b) What is the projectile’s speed relative to the observor?

## Homework Equations

## The Attempt at a Solution

Am I correct in thinking that I use the same method of Lorentz vector subtraction as shown near the bottom of the linked-to webpage below?

http://www.relativitycalculator.com/addition_relativistic_velocities.shtml

i.e. the section entitled, "

**What, therefore, would r & θ appear to be to an observor in relatively moving S'?**"

**Example 1**

Or does anyone suggest another (simpler?) method?

Thank you.

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