20.  A golfer hits a shot to a green that is elevated 3.0 m above the point where the ball is struck. The ball leaves the club at a speed of 14.0 m/s at an angle of 40.0° above the horizontal. It rises to its maximum height and then falls down to the green. Ignoring air resistance, find the speed of the ball just before it lands.

We want final speed.  We know total displacement in the y is +3.0 m.  We know horizontal speed will stay constant if we ignore air resistance.  We know acceleration in the y direction is –g.  We need to stick a minus sign in since the initial y velocity is up or positive, and the final is down so we will call it negative.  So we find the final x and y components of velocity and then add them as perpendicular vectors using Pythagorean theorem.

 

Horizontally, we get

 

For the vertical we do not know time, but we know y so we use equation

 

 

 

 

So final speed is gotten from

 

 

 

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This page last updated on January 11, 2020