Conceptual Physics

4.11 - Sample problem: a cannon’s range

Draw a diagram

Variables

What is the strategy?

1. Use trigonometry to determine the x and y components of the cannonball’s initial velocity.


2. The final y velocity is the opposite of the initial y velocity. Use that fact and a linear motion equation to determine how long the
   cannonball is in the air.


3. The x velocity is constant. Rearrange the definition of constant velocity to solve for horizontal displacement (range).

Physics principles and equations

The projectile’s final y velocity is the opposite of its initial y velocity. The x velocity is constant.

We use the following motion equations.

vyf = vyi + ayt

How far away is the haystack from

the cannon?

speed v = 40.0 m/s

angle ș = 60.0°

initial y velocity vyi

final y velocity vyf

x velocity vx

elapsed time t

horizontal displacement ǻx

acceleration due to gravity ay = í9.80 m/s^2

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