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Cannon Balls
Age 16 to 18
ShortChallenge Level 
Why do this problem?
This short problem is a reasonably routine application of kinematics; the interest lies in the numbers obtained and the questions concerning the validity of a physical model of constant gravitational force.Possible approach
Students could be asked to make an estimate of the speeds and heights before starting the calculation. Developing a skill and habit for estimation is very useful in more advanced applications of mathematics.Key questions
- What has the radius of the earth got to do with this problem?
Possible extension
Try the follow up problem Escape
from planet earth .
You could also extend this
to suppose that the balls are fired upwards on a
trampoline with coefficient of restituion 0.5. How many bounces
would it take for each ball to bounce less than 1m high?
Possible support
Provide students with the equation for motion under a constant force.You may also like
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