Help needed on Projectile Motion!

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  • #1
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A golfer on a hill 4.0m above sea level hits a drive at an angle of 20 degrees, but unfortunately slices it to the right so that it goes into the ocean! If the ball lands in the briny 5.0 seconds after it was hit, what is the initial velocity of the ball? What height (above the cliff) did the ball reach before falling downward into the water? How far from the tee did it travel? How much later will he hear the splash of the ball? Assume sound travels at 343 m/s.
 

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  • #2
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I am not even really sur ehow to get started with this problem!
 
  • #3
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There is an equation like
y = xtantheta - [gx^2/(2v^2cos^2theta)] where x is horizontal distance covered andy is vertical distance. Use this and report if you still have problem. Also try deriving the above formula.
you must also be knowing that t = 2vsintheta/g
 
  • #4
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Where did the equation involving the tangent come from? I do not remember my instructor going over any equations with a tangent in them.
 
  • #5
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First find t fromthe horixontal equation x = vcostheta*t.
then substitute t in the equation y = vsintheta*t - 1/2g*t^2
 
  • #6
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Juz letta me give u a little push in starting this qn..
It may seem like a 3D motion qn but it is actually juz 2D..

For the 1st part, u noe that the ball touches the water 5s after the golfer hits the ball.. u oso noe that the height (oso known as the displacement) above the water where the golfer hits is 4m.. u oso noe that the vertical acceleration for bodies in 2D motion is only gravity ( 9.81m/s^2) and what u wan now is the initial velocity.. note: <---this is vertical.. u still nid to get use pythagoras theorm on both the horizontal and vertical velocities to get the initial velocity..

I hope this gets u start off.. the rest shld be quite easy..
 

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