Posted by **Mima** on Sunday, September 16, 2012 at 4:52pm.

A soccer ball is kicked from the ground with an initial speed of 14.5 m/s. After 0.272 seconds, ts speed is 12.4 m/s. (A) Give a strategy that will allow you to calculate the ball's initial direction of motion. (B) Use your strategy to find the initial direction.

- physics -
**Elena**, Monday, September 17, 2012 at 4:34pm
v₀⒳= v₀•cosα,

v₀⒴ =v₀•sinα,

v₀² =v₀⒳² +v₀⒴²,

v² =v⒳² +v⒴²,

v⒳= v₀⒳,

v⒴=v₀⒴ -g•t,

v² =v⒳² +v⒴² = v₀⒳²+(v₀⒴ -g•t)²=

=v₀⒳²+v₀⒴² -2 v₀⒴•g•t +(g•t)² =

= v₀²-2 v₀•sinα•g•t +(g•t)².

sinα= [v₀²-v²+(g•t)²]/2•v₀•g•t =

=[14.5² -12.4²+(9.8•0.272²]/(2•14.5•9.8•0.272) =

=0.823.

α=55.35°

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