A cannonball is fired from a cliff top horizontally out to sea with a speed of 74m/s. The cliff is 320m above sea level. Calculate the speed of impact?

how do you calculate the speed of impact pls help!!

1 Answer
Nov 1, 2017

speed of impact=108ms

Explanation:

The question does not say anything about air resistance, so we are to ignore air resistance. This simplifies the problem significantly.

Therefore the cannonball's horizontal velocity, vh, continues without change. It gains velocity in the vertical direction according to the suvat formula

v2=u2+2as where

  • u = 0 because the cannonball is fired horizontally
  • a=9.8ms2
  • and s = 320 m.

Filling the data into that formula will give us the final vertical velocity, vv.

v2v=02+29.8ms2320m=6272m2s2
vv=6272m2s2=79.2ms

The cannonball's speed of impact is the magnitude of its final velocity. The final velocity will be the vector sum of its vh and vv.

speed of impact=v2h+v2v
speed of impact=(74ms)2+(79.2ms)2
speed of impact=11,748m2s2=108ms

I hope this helps,
Steve